Well look at this way,
PS3 + Good 1080p TV (1920 x 1080) + Games is approximately £2000
Gaming PC (8800 + Core 2 Duo) + Good Monitor (1920 x 1200) + Games is approximately is approximately £1800
You can do more with a PC, you can be productive, you can easily browse the internet, with fully working features like an AJAX enabled browser. You can run an OS without having to working about the nightmare of trying to optimise it for an asymmetric CPU etc.. etc..
So comparatively is it worth it? I'd say so.
Is it worth it to you as a person and your needs? For most people, no.
Yes but what I said was "if you include the price of the game(s) and the graphics cards + any other performance mods to be able to play"
So what I'm saying is, you can run the game on a pretty good machine, and it means you can do all sorts of other stuff on it, etc. But this graphics card, which would be a crazy price, since you say it's only use would be for games, would it really be worth buying just to get a good setting in a game?
Just as a note, I would also say that you would buy a high def TV for movies rather than a PS3, and a PS3 is just about the most over priced piece of hardware for what you get. But all this is just my opinion.