The last Billiards game I really enjoyed was "Ultimate 8 Ball" on the PS1... http://www.fileplanet.com/11347/10000/fileinfo/Ultimate-8-Ball
Looks like there's a PC demo... I don't know if it still holds up. Virtual Pool 3 may be better since it's more recent. http://www.amazon.com/Ultimate-8-Ball-PC/dp/B00001QHX6/
And that would be the full game (for under $3 used, not counting shipping).
I just remember that it had a variety of games to play, a variety of tables to play on (including nonstandard sizes, and shapes), a variety of locations/table styles, and a variety of AI opponents with their own style of play. The music was half decent.
If you don't mind playing against other players, 8 Ball Pool on Miniclip/IOS/Android is surprisingly good for free. As long as you have some semblance of skill you won't run out of the currency it uses.