For example... Beyond Good and Evil is cheaper on GOG right now by just a tad, but it includes a soundtrack and artwork with the game.

Although some games are similar in price, GOG often has little extras included that Steam doesn't. There are a bunch of games they give you access to for free when you make an account. Not sure if they are any good though...

Don't forget to check out the GOG sale too!

http://www.gog.com/