Assassin's Creed 2: Poor PC optimisation despite no real graphical innovations and no option to turn off shadows as well as draconian DRM made it unplayable for me. However, I plan to give it a second try when I get a much better computer. Ezio is too hot not to. Yes, Ubisoft, only because Ezio is hot.
Spore: Expected much more, especially on the creature stage. They could have made it a more complex survival aspect. As it is, creatures live in nests, food is plentiful and the only danger are the Epics. Boring, boring, boring! Also, I can't make a dragon fly properly.
Dragon Age 2: Reused environments, boring characters (except Varic <3), weird elves, weird story, no consequence to actions, lame rise to power and boring boss battle. I had more fun fighting Orsino than Merredith and also thought you should fight one OR the other, depending on whom you sided with. The idol thingy was pretty weak. Oh and "can't take three steps without mass genocide" - Toegoff, which I very much agree with.
Echo Bazaar: Limited actions? Yes, game killer for me. Also, the story and text seemed pretty uninteresting the time I played.
The Sims 3: It's gotten better with the expansions but the only reason I still play Sims 3 it's because of its open neighborhood and superior Create-A-Sim. Otherwise, the game looks like all effort was put towards the neighborhood and even that isn't as good as it could be. The "seamless" part of it needs AwesomeMod to help it (fast switching of households, saving wishes and inventory items on switch), as well as the weird story progression. As for graphics, they look a little better than sims 2, especially the sims themselves (no mods) but the objects look like they were imported directly from sims 2. Also, many of the sim-to-sim interactions from base sims 2 were removed. Also, sim larvae.
Minecraft: Granted I haven't played this multiplayer, but I did play an afternoon of it on single, made a pretty little pyramid... step pyramid that is. Didn't even try multiplayer since the first thing I wanted to build was impossible (a giant, normal pyramid).