Last [consoles] generation being XBOX 360, PlayStation 3 and Nintendo Wii. I agree about the PC having no "generations" to speak of. I suppose we can say the same for consoles, but it's just easy for most gamers to 'refer to' a specific time period for consoles, for example categorizing games (or consoles) of the "8-bit era", "16-bit era", etc.
Anyway, for the sake to discussion, between November 2005 (XBOX 360's release in NA), to November 2012 (Wii U's release in NA, effectively 'starting' the 8th generation) I would say that, all things considered, the very best games ever released during the last generation is in fact a trilogy, namely Mass Effect. It's essentially as important of a sci-fi universe as Star Trek was (perhaps still is) for its time. There is nothing else, in my opinion, that comes close to Mass Effect as far as science-fiction in video gaming goes. The only "equivalent" we have is fantasy-based and is the Dragon Age universe (trilogy).
I also want to mention that I would probably be one of the first here to bash on [most of] Mass Effect 3 specifically (except for its multi-player, which was great), but the overall experience from the entire trilogy cannot possibly be ignored. The original Mass Effect, along with Mass Effect 2 (not event including ME3) are both some of the very best video games ever created regardless of the "generation" they belong to. Just pick your favorite of the trilogy and don't even dare feeling bad for giving it a comfy and well-earned spot in the video gaming Hall of Fame.