What people find acceptable varies. Many people will consider frame rates under 20 FPS unacceptable, and 30 FPS and over is considered good rates, although hard core gamers might demand 60FPS for their games. Most current cards can do 20 to 30 FPS in the most demanding of games. You can always trade resolution for speed, but the fastest cards today can run most games very acceptably even at 1024x768. Current generation cards all support DirectX 6, and all have an OpenGL ICD, either in beta form or release form.
Some cards have a native API, and special game versions designed for it.
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.