The difference is that 1 crediting Ikaruga takes skills. Don't make the mistake of thinking that the time needed is why I think Dark Souls is tedious.
In Jet Set Radio, the later levels are 15-25+ minute behemoths and when first playing them, you WILL likely run out of time as you explore and figure where the red tags are. Even more so as you replay and learn the location of green tags for extra points, and concocting a route to get Jet ranking. But here's the thing. Every time I played a Jet Set Radio stage, I was learning something new: a new path, a new way to manipulate the game physics, until I mastered that game top to bottom. Even now when I play JSR, having mastered the game, I still fuck up now and then. Because it's that type of game.
With Dark Souls, when I die, there's often a 5-15 minute trek back to where my soul was, and I'm not learning a single goddamn thing, because I've already mastered the enemies that I'm encountering. That's boring. A few back stabs, a few heavy swings, some walking, and I'm back to where my soul was. No challenge, no hardships, no learning new ways to play the game. Just the same shit. That is not challenging to me, playing a game after a death should be a learning experience. It rarely was for me in Dark Souls.
I have no problem playing a stage for 20 minutes and doing it over. I do have a problem with doing that, while not being challenged.
1 crediting Ikaruga is a totally different scenario and a really bad comparison. A more apt comparison is beating Dark Souls without dying. That would be a challenge, and it still wouldn't make Dark Souls a great game.