Lately Avast has revamped their user interface and whatnot. Looks really nice. Stays out of the way, too. I think I tried Antivir or something one time and HOLY CRAP THAT ANNOYED ME. Yes, I know I can get the paid version, thank you, now get the fuck off my screen. >_>
That's about when I accepted that Avast was probably the best free option, since it didn't annoy you with any ads or anything of the sort.
That being said, I don't think I've had a virus or anything in a very long time. I just use Windows Firewall for the firewall. Don't really need anything else, in my opinion.
If you do happen to want to invest money in something that's better, though, the Norton 2010 package is definitely a good option.
But, it's just not really necessary. Even crack and serial sites are actually pretty safe these days (at least from my experience). A whole paid security package is just unnecessary. Just put adblock on Firefox, and you shouldn't really have any problem. Some people suggest noscript as well, but I feel that it's overkill, and more a hindrance than a help.
So, I suggest going with one of the free options people have listed. I use avast, myself. Norton is good, but a bit overkill/unnecessary.
On a side note, is proving you have rudimentary spelling skills really that important? (to people complaining about that extra e)
Edit: I read a little about the 360. Apparently, it's like the Norton <insert year here> Internet Security packages of the past, just revamped a bit, in terms of UI and whatnot. Should be pretty good.