Everyone's entitled to an opinion - That's why I'm claiming Unreal Tournament as the best ever with several close runners up, such as Halo 3 and CoD 4 & TF2.
But what I want answered is - why are people putting MW2 as the best FPS ever, when I can factually prove it is one of the worst games ever made (opinion

)?
(Including freeware, demos and interactive videos)
The hype was fantanstic, the first few days were great... but then it dawned on me that the campaign just sucked, mainly the part where it didn't quite tie in with itself, let alone MW1.
So, I tried spec ops with a buddy. It was average; no pros, no cons. I enjoyed what little it was.
Now for the thing we were all waiting for, the multiplayer.
Firing up online, I kicked ass with the M16's 1 shots... then decided it was overpowered, unfair and gamebreaking. Using the FAL instead; I managed to continue playing with only a bit of raging: M16's, super-explosive noob tubes, commando knife's like the user is fucking superman kinda' bollocked up what could've been a great game. Somehow, the gametypes also flopped: S&D - killed by starting tubes. Demolition - good concept, failed in general (how can scoring 4/6 bombs in a game make you lose?). FFA - boosting whores. TDM - shit spawns, op weapons vs. useless weapons, glitched lobbies, broken maps, stupidly broken hit detection.
This game hold now holds a title for killing most of my brain cells from pure, blind rage.
I tried sniping at one point, it went pretty well. I picked off the 12 year old campers and charged around the map wielding a 6 ft sniper at my hip like Mr T and a minigun. But that got boring pretty quickly. So I started using the riot shield with equipment. It can be truely touching when the only unity online os from a final kill cam on me, where my attacker shoots me through the bullet proof cevlar or knifes me without any contact 3 ft away and everybody in the lobby responds with a 'what the fuck?'.
All problems fall into one sentence. The game was just a complete catastrophe.
TL;DR (shortcut)
Where Halo aspires to balanced gameplay and CoD 4 uses it as a guideline, MW2 was anything but. Actually, it was next to nothing. It was about as lively as a cremated corpse in an incinerator, where the only thing resembling something it should have been, is that charred hand poking out of the mound of well-done body.
Bottom Line: The game was a sequal to a god, but was as much of a god as a hangover turd, in your pants.