So many people still love FFVII's boss music.
Yeah, but Dancing Mad, the final boss music from FF6, was so much better. In fact, Nobuo Uematsu has yet to top the score made for FF6, which is fitting as it is the best FF ever made and the last one made that doesn't basically turn everything into anime archetypes.
As for final bosses, they go hand in hand with my distaste for video game endings. They are usually disappointing. It simply feels as if they make another boss, they just take a LITTLE more to take down, though not much. This coupled with the fact that most endings are just something short or simple makes me feel disappointed with the end of the game.
Bioshock, for example, had a disappointing final boss, and then it felt as if the ending was just swiftly put together. Not only that, but the "good" ending was just too happy for the game. While the "good" ending should've been positive, yeah, it should have also been dark and sad. I know the perfect way to have ended the game, really, but they went with "y'know, let's just have the stereotypically happy ending". PAH!
Gears of War, the final boss was only really hard if you fought him on the Insane difficulty. Anything less than that and he was pathetic. Not only that, but the game could've used a whole other level, so the ending was not satisfying because I wanted more. I also can't stand any kind of boss fight that is solved simply by pumping lead into them (and yes, there ARE other options for shooters).
Though Halo 2 and Halo 3 lacked a truly satisfying ending, the original Halo had a great one. There really was no final boss, but the atmosphere and execution was excellent. You return to the same ship you started on, only now it is ruined and decayed. It gives you more of the feeling that, yes, you HAVE been a long way, that you HAVE gone through such a journey. Not only that, but this vessel that saved your skin the first time now has to be blown up. After that, what do they do? Well, they start the ending sequence, only part of it is interactive. You go Hollywood by hopping into a Warthog and being forced to speed your way out. Even now I find the ending to Halo satisfying, because instead of putting this stuff into a cut scene, they put it into gameplay. In the end you crash into a wall and have to hoof it the rest of the way to your only chance of escape, enemy blasts coming at you from behind. Play this on Legendary, and you'll really feel the adrenaline as your shields go down in no time. Then, when the cut scene starts, you feel the same relaxed feeling as the hero does, sitting in his seat watching Halo explode. It makes the character's feelings your own, and from then on you watch the ending cut scene, understanding how the Master Chief feels, and...are left satisfied.
It's funny, because Halo's ending wasn't much, but it was more satisfying than most game endings I've ever experienced. Part of it is because, well, you actually played a good portion of the ending yourself. Instead of relying on a final boss, they decided to go with a more Hollywood approach and a new variant of the Metroid ending. In the end, it worked very well. In fact, it worked better than most JRPG endings did for me, as it feels like most JRPG's think "long cutscene means good ending!"....which it doesn't. It helps, certainly, but it doesn't make for a good ending.
So, what am I looking for in a final boss? Well, anything, just as long as it helps me feel like I'm part of the end of the game. Halo didn't even have a final boss, but it had a very satisfying ending. It had the build-up with it, too. I also look for more than just "shoot enemy, drop dead". If the final boss is nearly invincible, and I have to instead use the environment to kill them, then I get a more theatrical feel. If fighting this boss is different than fighting any other enemy in the game, then I feel as if I'm truly fighting the final boss. If your shooter has vehicles in the gameplay, then make the final boss huge and only beatable by using vehicles. If you're an RPG, do something like EarthBound, where you had to figure out that one of the most worthless abilities in the game, "Pray", is precisely what you needed to use in order to beat the game, bringing in a very climactic feel. In fact, EarthBound's ending is probably the best, most satisfying ending I can possibly think of in a video game, including the final boss.
In short, games need epic, and the final boss always ties in with the ending. If your final boss is disappointing, then so is your ending.