Ok... where to begin?
Firepro is my favorite wrestling series of all time.
Yes they are worth getting.
Theres a bit of a learning curve/feeling out process when you first start to play. Even if you hate it first, I implore you to keep playing it. Once you get the hang of it its an amazing game.
All the wrestlers are fictitious, but theyre based on real wrestlers. They dont have the same costumes and coloring of their real life counterparts (they do in the japanese versions), but you can edit them to look like they do in real life. And you can tell who they are by their moves and taunts. Yes there are MMA fighters in the game. I believe theres even a multisided octagon like cage/ring in the game. I know there is in the console version, and Im pretty sure its in the gba games as well. The MMA aspects of the game arent as fleshd out as the pro wrestling, and they dont work as well as a result. If your only thinking of getting Fipro for the MMA stuff..... ehhh.... you might be dissapointed.
Its all sprite based 2D hand animated goodness. But that does give it a certain 'old school' look and feel, so be prepared for that. The gameplay is very deep, and the grappling system is timing based, its not about button mashing, and its not as random as a rock,paper.scissors type of game.
Theres an edit mode where you can make your own guys, and there are lots of edit formulas for your favorite wrestler or mma fighter available on the intarwebs. Lots of faqs too.
The first one can be had pretty cheaply, you can probably find it for under $10. So I suggest trying it out and if you like it pick up the second game. The games arent that different tho, so only get both if you really like firepro.