During my formative years, I played videogames on an MSX machine, using the keyboard. I had a joystick, but that was crappy and didn't afford the control you had when using the arrow keys. (And the MSX didn't have a mouse -- at least not the ones I used, so I never used a mouse for gaming.)
Then, when I got a PC and Doom came out, I played a lot of that -- again, using the keyboard. Doom doesn't have any "verticality" to it: you never can get to the same spot on different levels, except on elevator platforms. The technology just wasn't advanced enough to do that. The upshot of this was that you never had to adjust your aim vertically: the engine compensated for that itself. So all you had to do was to aim and shoot -- and the keyboard was perfect for that. I used to be pretty good -- not good enough to win tournaments, but I consistently completely dominated my flatmate and his friend, even if they cooperated.
Then Quake came out, and that had a more advanced engine -- one that did deal correctly with vertical displacement. That meant you also had to aim vertically (of course), and that is where the pattern of "aim with mouse, move with keyboard" started. And... I just never made that transition. I used to play quite a bit of Quake with colleagues on Friday afternoons, but since I only could play with keyboard and never learned to simultaneously aim with a mouse, I just never was any good.
(Now, with a controller, it's not so bad anymore, but all the "serious" FPS games are played on PC, where mouse/keyboard combo dominates.)
So I never got into FPS'es, and when the wave of online FPS'es came in, it passed me right by. I also mostly don't like the 'bro gamer' culture surrounding games like that.
And then recently, Playerunknown's Battlegrounds came out, and I caught someone streaming it on Twitch. The concept is simple: you get matched with 100 other players. You're all on a plane without equipment, and you can parachute out at any moment you want, landing on an island map with lots of deserted villages and other infrastructure. Then you have to find equipment (guns, ammo, gun modifications, armour, first aid kits etc). Every so often, the play area is restricted to an ever-shrinking circle -- and if you wait long enough, you'll take damage when you stay outside of the circle. Last player alive wins. There's also a mode with duos and squads of up to four players.
It's brilliant: everybody starts off at the same level, and it's a question of skill and luck to find the best loot and make the most of the loot you find. Because the circle shrinks, there's constant combat: you just can't camp on the high ground and wait for others to come and find you. It also means that a single round is about 30 minutes, so you can catch a round on the quick. Whereas watching other FPSes bores me, this is really amusing: during looting there's little tension (if there isn't another squad in the area) so the players tend to goof off, but that all changes within a second when shots are heard or a vehicle approaches.
(Still don't want to play it, because I'd be bad at it, but it's nice to watch on the second monitor as I'm doing other things, like writing an LJ entry...)
I've mainly been watching Scariel. He's very good at what he does (he is a professional FPS player for five years now), and he takes time to explain his tactical considerations when doing something. He plays the game very laid back: if he doesn't have to shoot, he won't -- shooting gives away your position and alerts others to your presence! We've seen him team up with people who never played the game before, and through his coaching, they even won. He's having fun doing it too, which is also good to see.
The other streamer that I watch is Anthony_Kongphan. Anthony is almost Sacriel's polar opposite: if he sees another player, he goes for it and tries to mow them down. He's so good that he often gets away with it too, but his play style gets him into trouble too.
And then there are the games where these two cooperate (often with two additional players to round out the squad of four), and it's absolutely fascinating to see how those two playstyles mix and how that plays out. It's really a lot of fun to watch. And since a round is only 30 minutes, it's easy to drop in and out of a stream, instead of having to invest hours to keep up with the game.