The most difficult game I've ever played was Radiant Silvergun (a top down shoot 'em up on Sega Saturn). The end boss took 2 players about half an hour to kill with infinite lives! The screen was so full of bullets that evading them for just a few minutes would have required a direct linkup from my brain to the CPU.
Now, this is simply not true... Radiant Silvergun isn't an easy game, but a hard shooter it is absolutely not. I got it half a year ago for my Saturn and it took me about 10 hours to complete the game.
First of all, you can set the difficulty, and it makes HUGE difference if one play it on an easier level instead of the harder ones.
Secondly, the game is built in a way so that even the beginner shoot'em up players can beat the game if they just keep on trying. The game keeps track of the gameplay time, and the more you play the more credits you gain (if you have gained 10 credits from gameplay time these credits will always be available when playing the game from the beginning if using the save). Furthermore, you gain credits (max 2 credits per session, though, if you manage to defeat a boss with 100% destruction ratio). Also, your weapons gains levels and after reaching level 40+ on most of your weapons the game becomes even easier to beat. High level on the weapons together with some gained credits will for sure make the game beatable even for the inexperienced shoot'em up player.
And, unlike games such as R-Type, where you die if being touched by a pixel of the shots or the enemies, only the center of the ship in Radiant Silvergun is what matters if being touched... thus making dodging bullets not such a big deal (compared to other shooters) even though the screen is filled with bullets at times.
Finally, two more things... the final boss can't take half an hour to beat, since it can't be beaten. You just have to evade its bullets for a certain amount of time (2 minutes, is it? Can't say for sure), until it self destructs.
If talking about the boss just before the final boss, the huge human-like figure running around on the ground, it took me about 7-8 minutes to beat it, in single player mode, with mid-levels on my weaponry. So, honestly, I can't possibly understand what you are talking about when claiming it to take half an hour to beat.
Maybe, just maybe, if one manages to reach the 'almost' final boss the first time playing the game, having only leveled up the weaponry during that very first session of gameplay, and having done it really bad I must add, it could possibly take as long as you claim, but if one has managed to get that far during the first gameplay session one would be so good at playing the game that beating the 'almost' final boss would be a breeze anyways.
EDIT: If you, and the one that you played with, played through the game with infinite lives and rushed through the game from beginning to end without leveling up your weaponry properly (or maybe even skipped directly to the final levels), well, then I can understand that there was some problems with the boss you were talking about. But the game wasn't designed to be played that way.
