Halo 3 is only a must have because of the massive online community, despite it's age. I think the only reason it's so large is Halo is such a generic FPS. Gears is awesome, but it can get repetitive. Other games you should play are...

Fallout 3, Oblivion, Call of Duty 4, Call of Duty World at War, Left 4 Dead and Bioshock.

All of them excellent games and in my opinion, with the exception of Left 4 Dead, all are Game of the Year materail, in which one of them is, unless Oblivion is too.

No. It's an "achievement" not a dollar you're earning. The achievements are for your own personal ego to show off. I kinda recently got a 5 digit gamer score and boy was I happy, sure maybe most don't care, but it looks cool for me.

At most, maybe if you unlock all the achievements, you unlock special armour or weapons.

I guess none of you have played Tales of Vesperia the asian way? By that I mean unlocking all those costumes, going through second playthroughs, because the one series I'd actually play through a single player mode over and over is the Tales series. You can get anywhere from 40-90 hours out of Tales of Vesperia if you play it the asian way. Play it the normal way, doing the main story, and some level grinding and you'll do it in about 40 hours.

I beat Fallout 3 in 25 hours, doing like half of the side quests and minor exploring. I did all the side quests and finished at 37 hours. I've yet to explore everywhere, but I got bored, so I'm going to trade it in.

I'm about to start Fable II but I heard it's short. Far Cry 2 is suppose to be a long single player experience that isn't particularly revolutionary, but entertaining. I've heard the multiplayer isn't to great though. But to be honest, I know you said you don't want multiplayer, but multiplayer is really the only way to get maximum hours out of a game. I LOVED Call of Duty 4, and I didn't get bored from pretiges 1-10. It took me 300 hours. I plan on doing the same with World at War, and if Gears 2 keeps coming out with new achievements and maps, I'll be happy.

If you're worried about spending money, trade in. This recession is hittng me too, so instead of buying I just trade in my stuff that's not part of my "essential" collection. Anyways, that's just my opinon.

Get Fallout 3 first, beat it in 25-35 hours, then once you got you're achievements if you just roll that way, trade it in and get Halo 3. Fallout 3 is an excellent game, but I didn't find much replay value in it and the additional content is probably awesome, but it's going to cost $5-$10 and it will probably only last an hour or two.

As much as I dislike Halo, the vast majority loves it, and as long as you have Xbox Live it will last you a long time.