Here are a few that come to mind for me:
Fallout 3
Skyrim
Red Dead Redemption
GTA 4
Minecraft
various call of duty games
Bioshock
Crackdown
Obviously, five of those are open-world games, with at the very LEAST, 40 or 50 hours of gameplay. I honestly felt guilty after getting games like Fallout 3 and GTA IV. It's like they gave me way more game than I actually deserved for the $59.99. I think if they initially charged $79.99 for those games, I couldn't really get pissed off at them, because I think their herculean efforts in those games was worth that. Those developers created gigantic interactive worlds to play around in. Pretty detailed and visually arresting worlds.
I'm not into the Call of Duty games, but my kids can play those things every day, for years. The gameplay is unending. It kind of reminds me of Madden '93 on the Sega Genesis. When Madden 93 came out in 1992, I could play that game for hours on end, every single day, for months and months, if not years. These Call of Duty games are kinda like that for people that are into them. I'm personally not a COD guy, but I can see the value there.
I'm also not into Minecraft, but I can see what it's done to the popular culture. My kids got it for Xbox Live, and they have put in redonkulous hours on that game. 90 percent of their friends have that game as well, and put in the same number of hours, or more.
Bioshock and Crackdown aren't particularly long games, but I just feel like they are two of the very best games of this past generation of gaming. Fallout 3 is actually my favorite game of this gen, overall, but Bioshock and Crackdown aren't far behind. I got way more than my $59.99 worth off those games.