>>111078129We talking just Hal or the entire Green Lantern Corps?
Hal by himself would probably be up in both power and in ethics with Thor, treating Earth as home base but helping problems across the local systems as needed. He'd be an upper-tier avenger in general, but I don't see him being able to take mid or high level cosmic threats alone. He'd be great in a team with some of the others, though.
The entire Green Lantern Corps. Would be such a considerable presence in the Marvel Universe that Thanos and other beings would have to contend with. They'd either have been wiped out by a stronger cosmic presence already or be at nearly constant war with them. I admit I don't know too much of the cosmic forces in Marvel, all the stories I read tend to be earth-centric, but I am aware there seems to be much more intergalactic conflict that the corps would be involved with. Not to say DC doesn't have much, just that the Corps would probably be busier in Marvel.
On that, there could be a number of interesting beings that could use a Ring. I can imagine Thanos trying to understand and utilize the power of the Lanterns.
