Won't it depend somewhat on what type of games you play? And do you want it to be multiplayer etc...?
I got a shock when my HD 4000 on my i5 could play Dirt Showdown smoothly when I had to briefly remove my 770.
Put it this way you're probably not going to be able to play current AAA rated games that came out in the last 18 months or so at the highest of settings if at all. But there is such a wide variety of games these days unless we know what type you want to play, the list is endless. I've discovered a lot of Indie games that will run on most onboard gfx based systems.
Don't forget to check out the demos available on Steam et al.