Mortal Kombat games are coming out at a clip of about every 4 years now. People get fighting games to play competitively. You'll find thousands of these people at the EVO tournament next weekend.
I imagine the competitive aspect holds water for FIFA as well.
Yeah, the sequel sneering in other posts in this tree is not a great look. Mortal Kombat changes significantly between iterations and while 2D fighters are not my cup of tea the depth and intricacy of the way MK11 plays is really well done (even separate from the self-aware and campy story stuff, which is good for a couple evenings of fun--we popped when the final boss threw a dang dinosaur at me!). Ed Boon and crew do good work and writing it off as "psh, sequels" is just not smart.
Some people just don't like sequels, or they don't like a genre and then all the hype about the sequels is for nothing (for that person). For example, I got nothing with MOBAs. Never had. Doesn't interest me. If I was younger back when these got popular I might've enjoyed them thoroughly but I grew up with Dune 2 and Command & Conquer.
I played MK2 and MK3 on the arcade back in the days. Looked it up, there were 2 years between those 2 versions (1993 and 1995). MK3 and MK4 I also played on PC, and MK4 is from 1997 (2 years again after MK3). So yeah, back in the 90s there were 2 years between each MK2/3/4. And MK (MK1) was from 1992...
I imagine the competitive aspect holds water for FIFA as well.