Apple has the infrastructure to deliver games, has tiny/medium/large touch devices that can connect via bluetooth in many customers hands (which already play games), and many many game developers familiar with the platforms. Every big studio has an iDevice team and there are hundreds of good iPhone games out there. If Apple can position the AppleTV as a console (maybe open it up to developers) or build something more along the lines of a traditional console, they will crush.
You can already do cool stuff like stream the game to the TV via airplay and use the device for a score/map screen (basically a WiiU) and it works surprisingly well and doesn't need cords or anything.
The only other real competitor here I see is one of the bigger android vendors like Sony or Samsung. If Sony could get the company in shape and stop producing products that compete with each other, they have many of the same advantages as Apple. They have android devices, experience making console/tv/etc hardware and even own game studios. They make every kind of electronic that goes in the tv room. But Sony has had this for years so that seems unlikely. They have already had huge employee slashes and are floundering.
Samsung has the same thing going on. They make everything and they have huge android phone/tablet penetration. I could see them easily jumping in on this and I hope they do. More competition blowing the doors of this stagnant industry could lead to a renaissance of smaller game studios.
EDIT I should add that Valve also has a chance here. There are many rumors swarming about a valve console or something similar. They have the distribution system and the games market experience, but have no experience with how to make hardware. Remember the last time that happened? I believe they called it the "red ring of death". I'm not saying valve can't pull it off but hardware is hard to get right. I look forward to what they do.