I watch Starcraft 2 a lot. Being a fan of TotalBiscuit does kind of help, considering i got started with the whole side of things through his beta videos on how he sucks at SC2. I play regularly, though i'm fairly bad still. Stuck in Silver league. If i had more time, i'd play more, but there we go.
I'm only really getting into the fighting game side of things more recently, it didn't take my interest as much, but some tournaments have been entertaining to watch. Like seeing the japanese UMvC3 player use Raccoon to decimate a couple of months back got me pretty interested. Still, it's a growing medium, and it's growing fast.
It is quite mad how huge the scene has gotten in the past year though. I remember watching TB cast some early matches about a year ago and it had maybe a few people watching it. Then you tune into the IPL4 last week and you get in excess of 75k people watching the finals between Alive and Nestea and you realise it's boomed. League of Legends is another one which has gotten big interest, but it has a larger playerbase, the only reason it has more viewers. It's dull to watch though, it takes too long for anything to happen. SC2 or fighting games, anything could happen fairly quickly.