I'm lucky enough to not have been really ill for a few years now; but I've always found action RPGs to be great for when you're ill. They're fairly gentle (on the lower difficulties, anyway), don't require too much concentration (get stick. Hit rat. Get bigger stick. Hit badger. Repeat), and tend to be easy enough on the eye. The hero's journey always makes a great metaphor for being sick and getting healthy, too - you start off weak, but get stronger and stronger as you go
Anything from Dungeon Siege to Torchlight to Diablo III (although, from what I've seen so far, D3 is very disappointing) would do it. Spiral Knights has a lot of an MMO strapped on top of it, but it's free, easy, and just charming enough to keep you coming back for more.
Hope you get better soon!