Not for those that demand more from their first-person shooters.
If you purchase Quake 4, expect the following:-
1) Pretty Basic AI.
2) Linear path. Always one green door, amongst many red ones.
3) The obligatory on-the-rails vehicle section.
4) Mostly corridor based blasting.
There is a place in the world for this type of game, and I am sure many gamers enjoy it, however if you are not one of them, be warned.
Please note that this review is based upon the single player experience only, as I have not played online multi-player. The chances of me playing the game through a second time are nil.
Overall I would say that it is worth a quick blast if you can pick it up cheap, but to avoid if you prefer more substance in your first-person shooters.