I think that in most games, keeping the same experience despite the resolution is crucial, so there goes either fixed resolution or scaling. Scaling has the problem that, oh well, it takes some time and must be done such way that the result is this likeable.

Showing more of the game world will work only for... how to say it? not much action-packed? games. I mean, yes, you can show more space in a shooter, but this will allow the player to see more, making the game easier for him. And if we are talking about multiplayer, perhaps... That is an absolute no-go, as it gives one player advantage over the other. Although this will work fairly for puzzle, or turn-based strategy games, where the gameplay is not affected by one's speed of reaction and ability to tonice things quickly.

My only other idea than showing more of the game world, in case of additional screen space, would be a bigger UI; possibly providing more detailed information (but rather not more information, in terms of quantity) and maybe some additional buffer/shortcut space.