I'm watching a friend play through the Metal Gear Solid series, and I've never played any of those, but mostly because they aren't my sort of genre (I'm no good at shooters/horror titles).
I love RPGs but can't really seem to get into Zelda for some reason. I own a few of the titles but I just haven't warmed up to any of them yet.
I also haven't played much in ways of Final Fantasy. I've played a lot of XII (but some friends say it doesn't represent the FF series well at all), but that's probably it. Never played VII. For some reason, I got pulled into Dragon Quest more than I did into FF.
Oh, and I've been playing Diablo 3 again because my friends want to do Reaper of Souls when it came out. I never played the other Diablos, so I have no idea what they're talking about when they talk about the storylines of the previous games.