Half-Life 2, Gears of War, Fallout 1-3, Planescape Torment, Knights of the Old Republic, Deus Ex, Counterstrike, CoD4, Starcraft to name a few more.

It deserves it when its a good game.
Halo: CE was a brilliant FPS, one of the best I have ever played at that time.
Halo 2 was also a very good game but it seemed they took a step back on the story to focus on MP, not something I would've done but still very good game.
Halo 3 was kind of a let down because they took another step back in the story department to focus on the MP. The graphics were sub-par but the brilliant controls were still there, I never got into the MP mainly because I had my PS3. And it shouldnt always be about the MP, if thats the case just cut out the story mode and focus on MP.
Halo Wars, from what little I have played of it was alot of fun. It actually made RTS games on a console fun to play.
This is all my opinion

No.. none of those games are better than halo 3, especially VP and BK. KOTOR is close but no match for the awesomeness of halo 3.

Lol, what can I do to make you see the light (No, not the blinding light of HDR from Halo 3) of truth? All the games I mentioned are by far greater then any Halo game. I have yet to even mention the delights of Zelda, Baldurs gate and Left 4 Dead.. actually scrap that... anything from Valve.

Actually, I think I'm gonna stop... I'm just listing my fave games of all time now.

Yes, I say they are all better than Halo. Why because I say so. Which seems to be waht you are doing. I doubt you have even played half of the games that Scoobes and I said. Now please tell me why you think Halo is better besides "it is the best game ever".

Oh leave Manos alone, liking Halo 3 best out of his collection is an entirely defensible position.

On a serious note, if that's true (not playing them), I suggest you do. The games I listed I feel should be on a list of "Games to play before you die". They're really good.

I'm not sure we are disagreeing...I never said all great games sell well (Valkyria, is a great game) or that all high selling games are great.  The combination of current sales AND reviews for the Halo FPS games is pretty solid evidence that it is in fact a great series deserving of it's popularity and acclaim. 

If the OP feels different, and has a better argument than "KZ2 > Halo" crap, I'd like to hear it, but the truth is, I don't think he does.  IN FACT, I'd bet he started this thread JUST so he could say Killzone 2 was better.

Don't know about Halo 2, didn't play it. Halo 1 and 3, don't!

Well, I haven't played VP:TIP because VP is the one of the worst games I have ever played. Also I haven't played planescape torment, just because I know it is not my cup of tea.

Why halo 3 is the best game ever? Because it is the most fun game ever! Duh. :O

Edit:

I have viva pinata: tip collecting dust where it belongs, at the bottom of a drawer. I was stupid to buy that game just because it was dirt cheap due to bad sales. I actually thought someone would trade a game for that piece of software. Silly me.