I have quite a few games I enjoy on my Nexus 7. I don't have many HD-specific ones (maybe because of the 7" screen, maybe because I owned a bunch on my phone first), but I think most fun games are just as fun on a larger screen.
One of the most surprising was Rayman: Jungle Run
because I'm not usually into infinite runners for more than a few minutes. I found that Jungle Run was really well done (and just as beautiful as Rayman Origins) and because of the constant moving I didn't have the same feeling of missing secret areas and stuff from normal platformers. I did go back to ace levels after a while, though.
I'm also a big fan of the racing games from Vector Unit (Beach Buggy Blitz, Shine Runner and Riptide GP). I wish Beach Buggy Blitz was more of a traditional racing game than infinite runner/driver, but it's fun for short bursts (and free)
Asphault 6 or 7 are also pretty good racing games if you're into that sort of thing.
And of course you have all the Angry Birds games, and Bad Piggies, and Amazing Alex from Rovio. I also think that Where's My Water is much better to play on a bigger screen than a phone.
Oh, and then there's the Kairosoft games like Game Dev Story, Dungeon Village, Kairobotica, etc. Those are all fun on any size screen!