>>>This post is a drawn out reply in another topic that I decided would work better in a new topic.
I like SOME bosses, but others I hate. In Chrono Trigger, some of the bosses have insanely large health amounts! Seriously, gotta hate long drawn out boss battles just because the boss has something like, I forget, 120,000 HP (or was it 12,000 or 1,200,000? I'll check the DS version sometime and get back to you on that). However, some bosses are the type that are typically fun, or there are some that are fun once you know the best way to do it, but before hand are quite annoying. It isn't exactly the most obvious thing that while you could pelt Draygon's stomach with missiles in Super Metroid, it's faster to break the turrets and allow him to grab you then use the grapple beam to attach to the electricity flowing from the broken turrets. What about Phantoon? Hey, how are we supposed to figure out that it is harmful to use Super Missiles?
Here's one of my staple fun/no fun bosses: Mother Brain (Super Metroid, not the original game's)
If you didn't get the reserve tanks and energy tanks, the boss is nearly impossible. Also, if anyone manages to get this far on three or fewer energy tanks, you are amazing, but sorry, there is literally no way to beat Mother Brain with this number of tanks because of how Mind Beam works.
I haven't played far enough into the game to say this for myself, but according to Mr. K, the boss on one of the areas in Legend of Zelda: Twilight Princess (something along the lines of Arbiter's Ground) is fun.
Cave Story's Monster X is annoying for first-timers because there is no obvious way how to damage it, mainly because you have to knock out the eye thingies first, which can confuse people if they notice they are attacking it in the most obvious way they can and aren't inflicting any damage. Once you know how, however, this is one of the funnest boss battles of all time!