I used to play WoW on a late 2006 MacBook when I was into that game and on the road. This was back when that particular MB was still considered new, so 2007'ish timeframe. When playing on just the internal screen, I had to keep all settings at the lowest level in order for the game to be playable... and it still played like crap. Oh how far Intel has come with their integrated GPUs. What a difference between the games I could play back then on that and the games one can play today on a current MBP with integrated graphics only.
If you're asking about playing games today on that, then I'd say you're limited to really old games only. The type of games that pretty much play on anything. That same MB today is basically only good enough for basic computing tasks, like web browsing (and even then it's sluggish).