The only boss fight I consider a push over was the final boss on normal mode. Dark Samus was way easy but as it was said above, this is because of how the hyper mode system was set up for that whole final portion of the game.
Normal mode should be just that . . . normal. Not easy mode.
But with that said, again, I found most of the boss fights to be quite challenging and even though the AU fight at the end was pretty easy, it was still a close fight.
As for what is said at the end, it's something along the lines of that the phazon threat is over, yet this victory is but a "twinkle of a star" spreading hope through the darkness or something. Pretty much, the fight against the phazon is done but it's a small victory lol. There is a large universe out there filled with darkness and Samus will eventually have to kick that darkness' ass . . . if you know what I mean.