There are few Glide only titles, but sometimes using Glide gives better performance. Games typically make good use of the features that the API provides. Most chips don't provide all the features, or they are not implemented perfectly, so the games don't look as good as they could on them. For example, the Permedia 2 lacks most blending modes, so has problems with coloured lighting in games. Table fog is another feature that is used by some games, but not supported by most older chips.
Some features just add a little more quality - antialiasing is the prime example.
Bump mapping is becoming more of an issue. Rendition 's V2x00 family is a good example.