I am willing to fully admit that Juggernaut should be near invulnerable and unstoppable. Fact is though, if there is one character in the Marvel universe short of Galactus that could beat him, it's Hulk. Both at their prime, yeah, you're probably looking at a stalemate, however in the long haul should one of them actually manage a win, I'd say it would be Hulk. In spite of Juggernaut's extreme durability, the Hulk gets stonger as he gets agrier, which means he's getting more powerful the longer the fight wears on. Since their is no upper limit to his strength, eventually you're looking at him managing to hit Juggs hard enough to do some damage. I hate to have to keep bringing this up, but if Onslaught could do it, then Hulk has the potential to as well, being the only character to not only hold his own, but cause physical damage to Onslaught.

With regards to how Juggernaut has been written in the past: yes he should be invincible and unstoppable, but what a character should be capable of and how they're written are two different things. Like it or not, it is the writer's who decide what Juggernaut is capable of, not your desires. So if the writers choose to have Juggernaut losing to characters he probably shouldn't be, then that's too bad, but it's the way it is. You might not like it, but then I don't like Apocalypse jobbing to every second string X-man to come along, or Darkseid losing to Superman in a head to head fight. Probably shouldn't happen but it does, and you just have to live with it.