I have mixed feelings about designations such as "FPS" and "RPG". What players would define as RPG is actually very counter-intuitive -- character customization, skill trees and skill progression, conversation options -- players are immersing themselves in the game, rather than playing a role (from this perspective Serious Sam is a role playing game and Mass Effect isn't). Actually that's completely irrelevant -- even if the name doesn't make sense (yes, its origins come from table-top role playing games, but seriously, that's such a small niche), I guess everyone has similar expectations.

On a more related note, "Fantasy RPG" can indeed vary so much, while "Sci Fi FPS" will usually tell you everything you need to know about the game. "Action Adventure" gets used a bit, but is ridiculously vague. I'd rather do without genres -- perhaps games would be less likely to copy genre staples and more likely to pick and choose elements that will work within the developer's abilities/vision.

But then when we don't have genre names we still create our own -- "GTA clone" is an older term these days. "CoD clone" is familiar. Remember "Halo clones"? Perhaps these were helpful in finger-pointing at those who copied a whole game (rather than copying elements from a variety of games, which is totally different and cool and awesome and leads to innovation), as long as the term isn't thrown around too liberally.

My definition of what makes a game a game may be binary, but I think that's good. In discussions as to whether or not games are art, my response is usually "Games are every medium that preceded them [music, art, drama, movies <which really contain all of the above>] plus interactivity."

I don't think I really stuck to one idea, but hopefully it still all makes sense