Depending on what kind of games you're into, The Underdogs has a great range of games, and most of them aren't very big in filesize. I'm pretty sure this doesn't break the board rules, as most of the games are legal to download and those that aren't supply links to where you can buy them.
One game off the top of my head that I can remember, is Beneath A Steel Sky. If you're into the whole point and click puzzle genre, it's definitely one of the best I've ever played and it's filesize is only around 70mb which considering how it looks and plays is pretty impressive.