PCs are good at browsing the internet, instant messaging somebody, typing emails, typing papers or reports, image editing, fiddiling with games (moding usually), and is arguably better at playing first person shooters (mouse aiming is easier than analog stick aiming). In general, you get work done on your computer and you can play games too there.
Now, a video game console PLAYS GAMES, and maybe other things (usually, the "other" things were possible from illegally diving into the console and modifing it to do things that it was never ment to do).
So, is the PC better, or the console? Here is the catch... the PC has to be upgraded for optimum gameplay. You are not guaranteed a certain framerate or responsiveness from the game. In general, you are not guaranteed to have a fun time at all playing the game. You would if you are up to spec... perhaps... A console has guaranteed framerates and responsiveness... if you buy that game, it WILL work as you think it should. Thus, a game console is your ticket to hassle free gaming...
There is a catch though...
Burnout Revenge is a good example of this. This game was released for PS2 and Xbox (I have the PS2 version) and it was released a bit quickly, some might say. It has some major bugs in it (your car sinking through the track into oblivion, for instance) and unlike the PC games that you know, you CANNOT patch the game. You LIVE with the bugs. This is supposed to mean that the console games will be made with a higher quality... but I usually don't see that.
Some games (God of War) shipped with GAME STOPPING bugs. In other words, this bug prevents ANYBODY from being able to finish the game. In those cases you are sometimes permitted to swap your disk for another disk with an updated game version (in God of War's case, you could).
Why buy a console? I am a fan of PC gaming but I was really frustrated at how I couldn't play many good games because they were console only releases (Burnout series, Star Ocean Till the end of Time, Destroy All Humans, Halo 2 (they didn't want another Halo on the PC... they wanted console sales)). So, therefore, it might just be best to get both and upgrade (the computer, or get newer consoles) every now and again. No matter what the choice, there is entertaining options on both platforms.