The match up of the early days was purely 1 base. The player who expanded often received punishment. 3 gate 1 robo, 3 gate 1 starport, and dt builds were often used. 4 gate was especially the strongest.
At the time warp gate research time was 140 compared to the now 160 seconds, leading to many 1 rax expanding terrans to lose. Hence terrans were contemplating on how to lead the games to macro games.
Open season 3 finals between MC and Rain showed a lot. The build orders of open season 3 weren't very generalizable because they needed to be as atypical as possible to catch the opponent off guard.
1.2. Marauder imbalanced?
Many of the players at the time had played broodwar. The standard unit of broodwar in TvP was dragoon, and it was about how one stacks the dragoon count while using it wisely. Dragoon of broodwar was a flexible unit.
Hence protoss players were producing a lot of stalkers. Similarly to broodwar, protoss players tried to find secure position through getting a lot of stalkers. However, the existence of marauder gave the players tragedy. Stimmed marauders with concussive shell melted the stalkers. Furthermore, the players who played sc2 with purely gateway units just like they would in broodwar were often crushed by marine marauder medivac.
At the time the imbalance claims on marauder were great, although now they only seem funny.
1.3. Unconditionally colossus
When protoss first appeared, there were many praises on the colossus. In fact, colossus was the only unit that could be used in TvP. Archons and zealots with speed upgrade hit by concussive shell were very slow, allowing these units to be kited very efficiently. Hence, in the early days, the metagame was based on holding attacks using sentries and stalkers to build colossus count.
2. MKP's fast expansion
Just as there was MVP's fast expansion in TvZ, MKP's fast expansion in TvP brought sensation to the match up. Previously, it was close to impossible to defend warp gate rush with fast expansion. However, MKP defended MC's 4gate by going 4rax after expansion in Zelnaga Cavern. This meant that after expanding, it's possible to defend the protoss rushes and hit them back with much better economy.
3. San - Discovery of High Templars (early 2011)
High Templars were neglected in the early days. Compared to broodwar, storm of sc2 had a lot smaller aoe as well as lower damage. Archons were very useful either. However, there was a progamer that realized the usefulness of khaydarin amulet and show how storms were used as soon as high templars were summoned. It was San.
San became popular for showing that he can defend any form of attack with just pylons cannons and high templars. A lot of games were produced by San only to receive a nerf with the removal of khaydarin amulet.
At the time Ghost's EMP removed all energy. However, with the removal of khaydarin amulet, EMP was also nerfed to only remove 100 energy.
4. 4gate nerf. 1/1/1. Prime's 2rax (2011 may~september)
The PvP at the time was very simple; who can 4gate better. Warp gate's research time was only 140 seconds and sentry production time was 42seconds compared to the now 37 seconds. Hence, it was pretty much impossible to defend 4gate without 4gating. Therefore, nerf to warp gate research time was given and the pylon area was reduced to 6.5 from 7.5.
However, as a result of this, 1/1/1 prevails. Before, Terrans had to be careful about 4gate when going 1/1/1. There could not be a good timing with 1/1/1 after making 2 bunkers to prevent 4gate. But, after the nerf to warp gate, 1 bunker was enough to defend anything, making cloaked banshee into marine tank push become extremely viable.
The TvP at this sate was very simple. If you want to win, just 1/1/1. If you want to practice macro and have fun, just 1 rax fast expansion. The winrate of TvP in GSL was over 70%. This was when there were 20 Terrans in Code S and 4 Terrans in WCG Korea.
1/1/1 was too strong to the point that protoss still could not defend it even if they knew it was coming. It is almost like PvZ immortal all in, where it is pretty much impossible to defend when the protoss makes no mistake in forcefielding.
There was another strategy that made life difficult for protoss. It was MakaPrime's 2rax. The player that could use this the best was probably Polt. reactor first into techlab 2rax pressure was very strong but did not slow the expansion all that much. Hence, it was one of the most powerful builds at the time, giving a lot of stress to protoss players.
Around this time, there was a nerf given to Terran with Archon becoming massive unit and its range increasing from 2 to 3.
5. Immortal rage patch (2011 september)
As the balance still tilts towards Terran, there was another patch given. The immortal's range was increased from 5 to 6. At the time the users thought it wasn't a big deal. However, this patch brought the end to 1/1/1 as the immortals started to be able to hit tanks. Although 1/1/1 still is a strong all in, it is dramatically weakened as a result of this patch.
6. EMP aoe nerf (2011 november)
Actually, there were still a lot of problems in the balance of TvP. Although early-mid game was strong for the Terran, even the late game wasn't too difficult for Terran due to the fact that EMPs could completely remove the shields of protoss army. Hence, the match up at the time for 200 vs 200 army was all about who can feedback/emp better. Nowadays it's more common to see ghosts trying to snipe HT. But before, needless to use snipe, ghosts really only used emp. So the nerf was given, reducing aoe of EMP almost by half.
As a result of this patch, there was a rediscovery of zealot + archon upgrade protoss, giving much strength to protoss and forcing terran players to micro snipe against HTs
7. 1gate expansion. upgrade protoss. zealot+archon rediscovery (late 2011 ~ early 2012)
After the immortal patch, a new build emerges. It's 1gate expansion. Although this build was used a lot in the past as well, it was weak against 1/1/1 and many other pressure builds. Protoss started to discover 1gate expansion into 3gates, making it the standard build now.
Also, Creator brings in the upgrade protoss, leading the build to be 1gate expansion -> 3gate -> robotics -> defend with 2~3 immortals -> double forge.
At the time TvP wasn't focused on upgrades. They were only pressed when they had some freedom. However, Creator shows that he could defend pushes with 2~3 immortals and get chronoboosted double forge, chargelot and archons to crush the opponent. Zealots with upgrade that were 2 levels higher than marines and marauders did not die and the damage dealt by archons were massive.
Protoss have begun to fight back the Terrans. A buff to upgrades for protoss even further strengthens their metagame at the time.
8. Terran's development. double medivac (late 2011~ early 2012)
It wasn't just protoss that was researching better ways to conduct gameplays. Terrans have also developed ways to hit sharp timing with 2 medivacs. 1 rax expansion into double medivacs with stim, combat shield and +1 upgrade led to many wins for Terrans
9. Parting's 1 forge + twilight council zealot templar. Upgrade Terran (mid 2012)
Upgrade toss was very strong, but there was one weakness, which was to be extremely defensive. By going for expensive double upgrade and immortals, Protoss could not deal pressure to Terran. Hence, Terran's triple expansion into double ebay was very strong against this. Also, because they have few stalker count, 2 medivac drop into multi prong harassment was very detrimental.
This was when Parting brings another metagame. He brought the build, 1 gate expansion -> 3gates -> robotics -> 1forge, twilight council -> no immortal high templar archive -> 2~3 high templars.
The reason why this build is viable is because one less forge allows twilight council to be built, whereas the resource needed for immortal is used to get zealots and high templars. From the robotics, he produced large number of observers to spread throughout the map. Also, the 2~3 high templar timing was equal the timing of double medivac, leading them to feedback the medivac and turn into archon to defend the mmm push.
The recommended match is parting vs mkp in gstl. This build requires perfect decision in micro. Therefore, while it is strong, it could lead to vulnerability.
10. Terran vs Protoss development (present)
There used to be claims that late game becomes difficult for Terran. However, there were many recent games where late game ghosts + vikings led to victories. Also, Rain has showed the use of warp prism, harassing Terran to its maximum potential.
There is no longer the timing of 25 minutes. The reason is because there is +3 attack cloaked ghost 22 minute timing. The reason why Terran's resources lack a lot in 25minutes is because they don't run 4th and 5th expansion. However, recently there are many builds were 4th and 5th expansion run smoothly. Perhaps, there is still room for development in TvP.