Assassins Creed 2 for me. I understand One had a lot of problems, but the groundwork was there for a good game. A Open world historic Hitman if you will, where the game has a specific mission to mission routine that you get into. Where it drops you into the missions and you're supposed to find a way through investigations how to kill the target. Each target is special with tons of way to go about it. They did'nt really build on the structure of the 1st one, instead it just became another open world game and I lost interests.
There's also MGS4 which is just a terrible disappointment. No game has disappointed me as most and I get kind of angry anytime someone praises it.
Mass Effect 1 is another highly rated game I don't get. I don't quite remember my original problems with the game, but I do know even without the technical issues on consoles, the game's combat is shit. It's wonky and simply not fun. It also had terrible level design, the level just looked and felt extremely bland. It's like they didn't even try to craft a place you'd want to see. Even the main hub world is boring and feels like a space mall more than anything. It dosen't help that side missions take place on copy and pasted "dungeons" that make Oblivion look like it has variety. The story could have been ok, but it quickly goes into generic ancient aliens crap. Sadly 1 is the best of the series.
Tales of Vesperia also. People act like its the best jrpg ever. Yeah it looks great, somehow better then all the rest of the Tales games this gen. But outside of Yuri, the cast sucks. The story is nothing great. The world is that now tired generic Tales medieval fantasy world complete with the same battle system from Abyss.