I'm going to have to give my vote for Halo. To say that it is a revolution in FPS design is an understatement. What Doom did for the genre in the 90s, Halo did in the 00s. The game's mind share was massive, so much that "Halo Killer" replaced "Doom Clone" for upstart titles that vied to be the next big thing. So many things we take for granted in the genre were either pioneered or popularized by Halo, from the "left stick moves, right stick looks" controls to the two-weapon limit to having melees and grenades put on their own dedicated buttons (the "Golden Tripod" as Bungie called it) to the well-integrated vehicle combat.
Commercially, it did very well and had incredible legs, and had a massive attach rate, with half of everyone who bought an Xbox in the system's first two months having also bought a copy of Halo CE. It's tied with Perfect Dark for highest-reviewed FPS of all time, and it won multiple Game of the Year Awards. It also single-handedly put Xbox on the map.
Personally, I think it deserved its success. It was incredibly fun, and it still holds up. I still routinely play Campaign missions, and it's still my favorite Campaign in the series. And I had a blast playing the multiplayer on LAN back in the day.
Visit http://shadowofthevoid.wordpress.com
In accordance to the VGC forum rules, §8.5, I hereby exercise my right to demand to be left alone regarding the subject of the effects of the pandemic on video game sales (i.e., "COVID bump").
