I used to be an avid PC gamer, and I have the PC to prove it - 7800GTX in SLI, 2GB RAM, dual Xeons (thats for work, not gaming

), 20" LCD, etc. I've dabbled in a few console games, Red Faction a while back was a high point (not the second one, the original

), GT3, Halo 2, few other games. I got a free Xbox with a projector early last year, spent about £50 on games & accesories, played it a little then it just gathered dust. Then someone gave me a 3 month Xbox Live trial, so I got Conker Live & Reloaded, and replayed Halo 2. There was a LOT of potential there, enough to convince me of the merits of consoles. However, I was still planning on keeping my PC at least mid-range to carry on playing games on my PC, the Xbox would handle the rest.
Then along came the X360, I couldn't help it and bought one 3 weeks ago. The X360 can't be compared to any other console, and all the PC gamers who are banging on about the PC being superior etc. probably haven't actually played on one. High definition is a big thing MS are pushing - and with good reason, it brings their console up into high quality imagery that PC gamers have been enjoying since '98 or so. So we've got sharp visuals, next we've got a service for centrally distributing FREE demos without waiting in download queues, without searching for the demo, and without paying any money at all (Silver service is free). You've got a centrally-based multiplayer system thats rapidly maturing (it looks like future games will finally feature dedicated servers, an essential feature for real multiplayer games), with player ratings, proper working voice coms, and so forth. Even the controls in games are mostly preset based on your settings in the dashboard (you set the controls for 3 separate genres in the dash, and the game uses those settings).
So lets compare this to a PC (as neutral as possible).
You purchase a game, thats £40 (online) for a X360 game, and probably £25 (online) for the PC game. They arrive and you put them in to your machine.
The X360 game comes up in about 40 seconds, ready to play (including console start). You start up the PC (30 secs) the PC game comes up with an installer, you click OK to all the agreements, type in a keycode, wait 5 mins or so for it to install (assuming DVD and not multi-disc), and then if its starforce, you reboot (potentially another minute). However the load times on the PC game are potentially faster than the load times on the X360.
The X360 game has the controls and visual settings already set courtesy of the dash, so you select campaign, press A, and let it load. The PC game requires you to set the resolution, customise your controls, change the mouse sensitivity, possibly modify the audio settings (Miles Fast 2D, DX, DX Hardware, EAX2, EAX3, EAX4, A3D), and then you get to campaign, and fire away.
The PC game has a series of mods and custom content available to download from the net. Sure it may break the game (or even your PC) but there can be a lot of it (UT/HL), and its all free. The X360 game will have some extra content available, but unfortunately it won't neccesarily be free. You may end up spending £10 or so on extra content that probably isn't as good as whats available for the PC game.
The PC game has multiplayer, but no ranking system, and no matchmaking service. The X360 game picks up on your friends, and if they're playing online the server they're playing on, you'll join too (if there's space). You can elect to prefer servers with other's you've met online, without needing to add them to your friends. This list of friends & preferred people is persistant across ALL of your games. You can send messages (both text and voice) to them at any time, and they can read & listen to them within any game. The PC version has none of this unless your friends use a specific service like Gamespy, and even then if they're not logged in through it, it won't work. The X360 game keeps track of your scores in different levels, so you can compare your ranking against everyone else. The X360 keeps track of your achievements so you can see how you're doing in the game in general compared to your friends, and other people. If the game supports it, you're skill is assessed, and given a number - your 'TruSkill' ranking. When you join a multiplayer game, you're put in with people of a similiar skill to your own, so you don't end up with a bunch of n00bs, or a bunch of maniac killers who can get a headshot from 100m. If anyone cheats they're banned from the ENTIRE SERVICE indefinitely. They can no longer play ANY games online unless they get a new account.
The PC game itself is cheaper, but the PC is much more expensive. The PC game is more hassle, especially if the game doesn't like something. You might have to update your drivers... again, you might have to install a new DX, you might even need to buy a new component. With the X360, updates come through Live, the last update I think took about 2 minutes (from initial on), it autoinstalled, it autorebooted, and I was good to go.
Realistically, to keep up with medium quality in games you either need to update to a mid-range graphics card each year (£150-£200 now), or a high-end every 2 years (£300-£400 now). You also need to upgrade the CPU (£100-£200) every 3 years, which requires a new mobo (£100), and possibly new memory (£100-£200). You have a couple of problems each month, maybe something corrupted, maybe a setting got messed up, etc.
The X360 is much more than your standard games console, it has a lot more going for it, and most of that comes from Live. However, a PC is still a very useful thing to have around, but if you remove games from the equation, suddenly you don't need such a powerful PC. You definitely don't need to keep upgrading, which is a big chunk of change.
Cheating ruined a lot of games for me online with the PC, but with the Xbox you know that no1 is cheating (you may come across 1 person, but they wont be around for long). This is a big thing imo, and a major reason I play online with my X360, but not with my PC. Voice coms help too
For me, a hardcore PC gamer, I don't plan on buying many PC games anymore. Many will say the pad sucks for FPS, I sure did (check my post in the 'should X360 have keyboard/mouse support). I no longer think that is the case, I can play an FPS really well with a pad. I completed Q2 on the X360 today, using the pad, without any aim support at all. With 3 USB ports, support for a keyboard and mouse is no problem, and I hope they'll support them in RTS games, but no other games, for it would ruin it for the pad users.
Anyway I think I've said enough

Hardcore PC gamer > X360 convert.