This article describes me, as a gamer.

Just replay the game as many times as you need! This is the only option.

I totally agree with the part about the final boss usually being disappointing, though. So much... It's quite challenging to ever create something that can live up to one's expectations and surpass all else you've encountered, giving you that fulfilling feeling of "wow" after it's all said and done. Stories of all sorts suffer from this problem. Endings are the hardest part to pull off successfully.

I replay games a lot, but that gets kinda old sometimes.

While I second you in the part regarding boss fights (NYX I'M LOOKING AT YOU, FU'CKING PERSONA 3), there's always alternative bosses in games I really liked. Well, you can't say Minerva in Crisis Core for the PSP was actually challenging, for example, but you needed to be 100% prepared and like at the ultimate stage of character's abilities development to go beat it. That's the only thing I feel like rewarding in games nowadays.

Eh, I just try to enjoy games and leave aside that feeling of unaccomplishment so I can be happy.