i used to have nightmares about ruby and emerald weapon in FFVII

Last bosses weren't always throwaway fights you were assured to win. The NES in particular had a lot of games with last bosses that were quite hard. And some more modern titles like Brave Fencer Musashi have taken a stab (only somewhat successfully) at making a last boss that requires some real effort to beat. And then there's the likes of Arc the Lad: Twilight of the Spirits, where the last boss is more than happy to turn you inside-out if you don't fight the battle exactly right... There's a fine distinction between challenge due to variety and challenge due to unbalanced design.

I would say majoras mask was a lot harder than the 4 temple bosses in Majoras Mask.
Gruntila was a very tough boss in Banjo Kazooie

not that I have finished it but I have heard that Dark Samus in Metroid Prime 2 is quite tough.

Truthfully I don't seem to have that much of a problem finding difficult final bosses. Quite literally the last six games I have played have all given me difficult final battles. The last six games having been.

Naruto Rise of a Ninja
The Orange Box
Assassins Creed
Fable
Mass Effect
Blue Dragon

That said none of those bosses felt like a let down in respect to that game. They all tested my metal as in skill, or stamina. Some of those final battles taking up almost an hour of game time. Fifty minutes I spent in Fable beating the final boss. Blue Dragon kept racking up the difficulty throughout the final battle. The Orange Box every final level was just plain sick. God I hate Striders. Assassins Creed I died a lot. Mass Effect was solid a gauntlet followed by fighting a wicked wall crawler could have been more intense, but it was on par with the other major battles.

Your not picking the right kind of games. Your playing games guaranteed to take it easy on you. Mario and Zelda games for instance aren't the best place to find the best final boss battles period. That is a constant your going to find more challenging battles earlier in those games. RPG games have to be much more forgiving, because the final battle can be with characters of vastly different levels who might have vastly different gear. Somehow it seems rather shabby to send a low level player back out to grind.

I would recommend you pick up Scarface for the Wii. Those are wonderful boss battles. They are always entertaining, challenging, and you feel very satisfied after you finally finish them. Give that game a try it should give you some satisfaction.

its kinda hard in rpg's. most games have lots of side quests, so either u 1) do all the side quests to get a high level and extra stuff 2) do massive grinding 3) make the bosses possible without the side quests making them easy.

A better question would be why are bosses being forced into the endings of games that don't need bosses (see Bioshock, Uncharted).

Maybe i am just bad, but i didn't think the last boss in Metroid Prime Corruption was exactly easy

An hour is just too long. 10-15 minutes is about right, anything beyond that gets in the way of something called Real Life (TM, Pat Pending). You know -- jobs, families, partners.

DMC3, MGS3 and FF12 all have 10 minute final bosses, and that's one of the reasons they're great games.

The whole idea that final bosses should be Ueberchallenging or close to impossible is a hangover of the earliest coin-operated arcade games, which were designed to extract as many quarters from players as possible.

@Slorgnet

Even the long battles I alluded to allow for saving during the contest. Blue Dragon for instance allows you to save right before the final battle, and I believe five times during it. Valve get ample save points in their final battles. Naruto the same as with Mass Effect which will auto save right before you fight Sovereign. Fable I confess I totally crippled my character in development. I had little to no ranged combat ability thus when the second half of the contest turned to ranged fighting I was fighting at level one when I should have been much stronger. My magic attacks were utterly pathetic, but with enough time I finally brought him down. Ironically someone a week later told me all I had to do was pull back on the bow for a few minutes and let the arrow fly.

Which raises a valid point that was somewhat overlooked the player always has the option to make any aspect of a game challenging. I remember playing Goldeneye upside down, or finished the space station in Shadows of the Empire without gasp leaving the interior of the space station. Did I miss a meeting have my fellow gamers lost the will to take it upon themselves to make games more challenging for themselves. We used to brag about such things.

Personally the only thing I dread with final bosses is throbbing weak spots. Somewhere along the line I have gotten sick and tired of this. Give me the option to win through attrition. Let me fight how I want don't hem me in. Let me use all of my weapons not just the one your going to let me use. Give me more then one way to take the enemy down. Let me find the bragging rights.

A example is how on rails the Zelda series has gotten with its final boss battles. The same thing every time you can only beat Gannon in one specific way and no other. Find out how they want you to do it, and then rinse and repeat three times. Usually to get to the point where you need a new trick find it and repeat as before. Twilight Princess was tragic in that it just copied the previous games and made you go through a handful of sequences. Somehow that final battle feels more like a chore then an enjoyable experience. I doubt anyone who has played the game will disagree. Some might say its somewhat difficult, but its doing so in the lamest kind of way.