Games that haven't been de-throned.

I'm trying to create a list of the oldest games that still excel, or are the best, at what they do and have not been dethroned by newer games.

How far back can you to a game that is still the leader in it's field? (Old could be 10+ years ago or it could be 5 years ago...)

Edit: So, uh, this kind of exploded! Thanks for all the responses - I'm making my way through the posts and checking out the suggestions