Yeah, pretty easy, but I STILL think X-Samus (original and mutated) was just as easy. I agree to the remark that Omega Metroid was nothing more than a plot device, not a boss. Ultimately I thought that all of the bosses were a bit...easy so...
For underwhelming final boss battles I'd have to agree with the remarks about PoP:SoT. Perhaps I'd say the same for Tales of Symphonia, while it was a good fight, it wasn't anything remotely special, and it was probably easier than some of the other battles.
The Motherbrain in Super Metroid was somewhat underwhelming now that I think about it. Actually, a lot of final boss battles are pretty damn underwhelming; Zelda ones however are still pretty damn epic.