ha....you guys are funny. Yeah if LucasArts had to make a victor it would be the Jedi. With Maul killing old Obi first, igniting a flash of the dark rage within Luke.
But with skill alone...using the knowledge we know of Maul through EU and film, Maul would have off'd Luke's green ass fast with a couple of lightening flip, kicks, force throws, dark rage....then focused on Obi, if Obi was still that fast and adaptable with his saber....Maul could have used some lightening, and with Maul's still growing Dark Force skill he better hit Obi with the lightening since his control over the Dark Arts would be not to it's full potential yet
is he older and weaker? or wiser and with a mastery of the form frobo? yoda is 900 years old and he owns like crazy. i doubt obi sat around in the desert doing nothing forever, he's a Jedi, he probably trained somehow. if i remember right we saw him take on the sandtroopers in ANH right?
old obi>maul luke doesn't even need to be there. he could stand on the side and watch...maybe he would learn something about saber fighting that way.
underestimated? i think overestimated, which perhaps proves your point. but seriously, maybe as a fighter, he's...hmm...mediocre at best. as a Jedi...pfft..don't get me started. he talks like he's some big good guy that will never do evil...and then he fights his own father and looks like a sith with a green saber. it's like dark rage or something.
i don't know, i hate luke and pretty much all the crappy stories after ROTJ. even the OT isn't my favorite.