The last UFC games from THQ did pretty well and while EA Sports MMA didn't do as well as UFC Unleashed it showed that EA Sports has the chops for an MMA game. Then again, EA Sports and Bioware are the only two EA entities that haven't dropped the ball particularly hard--of course EA Sports makes the exact same game every year and tells people that improvements were made to AI, scramble to find a new feature to add, and mess with the graphics.
Back to EA's foray into UFC, it's far from a dumb move. UFC is wildly popular and there's potential to do more with a combat sports simulator going with UFC than another Fight Night.
1. While there are many nuances to the sweet science, compared to MMA it's one dimensional. It's an arm of a larger combat sports beast. Doing a worthy MMA game would present more of a challenge to work through and put more content in--especially with UFC alone having several TV shows.
2. With specific licensing of the UFC brand they can run with a more concrete roster of fighters since they're all under contract to this one organization. With Fight Night, they couldn't even recognize actual belts, MSG was just called New York Arena, the rosters had some current boxers, a bunch of generated boxers, and legacy'd legends to put them in the game.
Since boxing deals more with commissions than organizations, it would've been difficult to get every top ranked boxer in the game. By Champion they managed to get more licensed boxers, but you're still not talking a concrete roster given that's 50+ across several weight classes.
3. EA probably feels they've done enough with Fight Night at the moment (which is far from true there's more to be done). When the series started in 1998 as Knockout Kings, it was coming out yearly until 2006 then they spaced it out with Round 4 and Champion. UFC could be EA trying to get back into an annual release situation.
Personally I liked the direction of Champion. The series had gotten stale by Round 2 and it just didn't make sense to keep releasing them annually (with most sports titles it doesn't make sense to keep releasing them annually when they could update the roster and go every 2 years so that significant improvements could be brewed, but whatever EA). EA knew it had to go a storyline route with Fight Night and it was a good story.
I didn't care for Legacy/Career mode in older games after awhile because you had Ali in his 30s, Tyson in his 20s, Lewis, Foreman, etc. popping up to face boxers in the 2000s. It's like "Yes, I want Ali and Tyson in the game. I want Butterbean and Joe Louis as well, but I haven't seen them since Knockout Kings," but they shouldn't be in the mix of my age appropriate boxers.
A remedy to that would've been bringing the Franchise mode from their team sports franchises and having you manage a boxing camp to breed future champions from the 1960s to present. You'd just have a stable of champions...then the legends pop up when they debuted, start tearing ass through the weight classes, and retire whenever. You could face the HOFers in exhibition or your Franchise mode.
Anyway Fight Night is a good franchise and there's a ton of improvements to be made (I'm going to submit some to EA's Game Changers), but it's UFC's time now.