Mar's M&M's,no seriously Might and Magic as it's always been know as M&M.

Games that lived up to the hype? God of War (2018). Skyrim. DOOM. The Witcher 3. That's about it.

Indies:
Guacamelee!
Broforce
Hotline Miami

AAA:
Bioshock 1
Batman: Arkham City
Borderlands 2
Civilization 3,4, or 5 (whichever is your entry point)
Left for Dead 2
Portal 1&2
Skyrim
Saint's Row 4
The Witcher 3

It's more of a difference between absolute versus relative experience. Let's say game A has hype is 0.5 and final game is 0.7, it's a +0.2 difference so net positive. There's a game B hype was overdone with extreme marketing promising 3.0 and the end game ends up with a high value at 2.5 it's still net negative of -0.5. You will enjoy this amazing game more than the first (2.5 vs 0.7) but the relative expectations of the first game compared to initial promises will be higher therefor the surprise factor will influence the experience (perhaps more so in the beginning as the effect is still lingering, over long-term it will likely matter less).

Anyone with a degree in psychology, please correct me if I'm wrong as this was only speculation on my part.

Absolutely agree with World of Warcraft. If you were there when it came out it was just an amazing experience (bar the tech issues the US launch had). One of those games I'll remember for the rest of my life. (despite stopping after 2-3 expansions)

Just think that, before WoW came out I mostly got disdain from people when I talked about playing a game I had to pay monthly for just to play it (Dark age of Camelot at the time), yet not only did WoW draw in more players than the (western) MMO genre had ever seen before (over 10/20x) but it actually got them to pay monthly for it, which was a huge black mark up until then. If you had asked me before WoW release whether an MMO would reach a million players I wouldn't have even taken the question seriously, it was that unthinkable at the time, yet WoW not only broke that barrier, it went beyond 10 million.

I feel the same way. In fact, I'm still hyped to play that game and I watch the trailer. I want a re-master but the way Rockstar is going nowadays, I'd say that modding San Andreas is much better than anything Rockstar could do to it with Social Club being mandatory now.

Basically everything Telika wrote apart from Assassin's Creed (too repetetive and boring in the long run)

A more recent example is Overload. That is totally justified in being hyped as Descent 4. Hell, it's more Descent than Descent 3!

Also Baldur's Gate deserved all the praise it got and it did revive the CRPG genre.

And basically all Origin games from the time when Origin was still an independent company. Unfortunately it went down the drain fast after being acquired by EA.

Personally, I found Baldur's Gate to be rather disappointing, particularly since it has all the issues of low level AD&D (which is not fun when every attack has like a 50% chance of missing), and the battle system is worse than the turn based battle systems of other RPGs.

Also, the CRPG genre was not dead; you still had games like Final Fantasy 6 (3 in US), Chrono Trigger, and Super Mario RPG, not to mention some lesser known ones (Lufia 2 comes to mind), followed by (the also disappointing) Final Fantasy 7, whose (undeserved) popularity led to the localization of such games as Final Fantasy Tactics and SaGa Frontier (a game I love to use as a comparison when talking about Baldur's Gate, actually, though the games are *very* different). Perhaps Baldur's Gate revived that specific branch of the CRPG genre (party based WRPGs), albeit in a somewhat mutated form, but that's not the only branch of the CRPG genre, and the JRPG branch certainly stayed alive all those years.

Minecraft. Yes, the vanilla game gets boring very quickly, but holy fuck are there a lot of amazing mods for it. My personal favourite are skyblock maps, where you start with nothing but a patch of dirt and a handful of saplings and eventually build a massive automated factory.