Golden Sun: Dark Dawn
This one sticks out because the rest of the game was so mediocre. Finally, you get a boss that's actually hard while some of the best music in the series is playing.
Sorry, but Dark Dawn was NOT mediocre. It has to be one of the best games I have ever played. The graphics were amazing, I loved the music, the characters were cool (But, as it was my 1st time playing the series, it took me a while to work out what happened in the 2 previous games), boss fights were amazing, the plot was amazing, and basically, the game in total was amazing.
I was going to say this game, but only because it was 2 fights in a row, but you were allowed to heal in between them, and then using Iris on the boss (after beating Dullahan) is ultra satisfying.
Also, the final boss of Okamiden was cool, as you got to fight your 1st companion, as well as a dark Chibiterusu.