He is the definition of a glass cannon.
I'm not sure where the glass cannon idea is coming from. We're talking about a robot modified for combat, who can take multiple hits from other modified-for/straight-up combat robots that shoot swords, fists, fire, electricity, etc. He can die outright die from extreme falls, environmental impalement, and being crushed, but that's about it. (I would also argue that death spikes are specialized, heavy duty constructs that are not synonymous with any generic pointy object, or else Needle Man would be the most broken Robot Master in existence -- but really, they're just game shorthand for don't-step-here.) Could you perhaps provide some examples of what you're thinking of?
Also, if we were talking about Proto Man I might agree; in Mega Man 9/10, he takes twice as much damage as Mega Man does in exchange for being able to charge his normal shot. Unless he's a double glass cannon?
He is pretty damn powerful but he has little defense. Ripley is crafty, she would find a way to exploit that. She has solid mechanical skills and could find a way to disable Mega Man's suit I'm sure.
I agree with you here, in the sense that Ripley is very smart and can use the environment to her advantage, and Mega Man is more of a "good is dumb" type. I'm not entirely clear on what you mean by mechanical skills though, and I'm not sure how Mega Man's armor would be disabled (unless you mean punctured/torn apart/melted/etc?). If you wouldn't mind providing an example here too, it would help me out a lot.
If she has access to the exoskeleton thing she used to defeat the Xenomorph with in the movie then I say she takes this.
Don't forget that Mega Man has access to all his Robot Master weapons, including Super Arm (which allows him to lift and throw chunks of walls, boulders -- a strength boost). I'm not sure how the weight of Ripley + Exoskeleton compares to solid chunk of rock, but as it's a robot endowed with extra strength, I feel Mega Man would be able to put out just as much, if not more, lifting power. He's also a more compact target, but that might not be as much of a factor.
But I mean, I think this is exaggerated by the differences in the level of technology of the worlds of these two characters. Ripley's future-earth has space travel, cryogenics and rifles that fire bullets, while Mega Man's future-earth has teleportation, time manipulation and robots that fire just about anything. Would you really say these things are on the same level, especially in terms of combat?
And really, does Ripley even want to fight? From the entries I've seen (Alien, Aliens) that she is not one to crave battle, and only really takes up learning how to use weapons to kill the Xenomorphs, which she loathes. I don't see any reason for her to risk her life in this or any subsequent fight in the tournament: there's no one to protect, and I don't think she particularly cares about the result as long as it includes her being alive. And Mega Man won't want to fight her, either.
So, unless the other Alien movies cause Ripley to hate everything robot, I think the real questions here are:
1. Who can be incapacitated more safely?
2. Does Ripley want to face additional life-threatening situations?
In the scenario I'm seeing, where they both realize neither wants to kill the other and they start talking, I think it would actually be safer for Ripley to deactivate Mega Man -- he could possibly direct her how to put him into some kind of sleep mode and she would move on. Having Mega Man use weapons on her would riskier -- even nonlethal weapons like Chill Spike or Spark Shock could be dangerous to a human, as their nonlethal effects are originally in reference to robotic targets. It may be conceivable that he could modify them for a human target, but that could be a bit of a stretch.
Is this all sounding reasonable? It makes perfect sense to me, but then again I'm the one thinking it up...
Naw dude, he's constantly fighting bosses like this:
Mega Man's never heard of Storm Eagle -- that's X's realm of expertise.