Well, you could run through the Madam Web vs The Collector event. In which various spidermans or put against different problems through out the multi-verse in order to solve them and beat the 'game'. There's also the secret wars events, I believe where worlds are colliding and collapsing and...
Well, if you were going to make them two different sections completely there should probably some form of strong tie in that would through narrative attract the sections together. Maybe they're a group of game testers who need to try out a bunch products/projects before they're release and need...
Does the medieval one include magic or is it simply all skill based for the most part? I am still kind of curious as to why two main MMOs since it kind of split things up. Are you planning to just to have two different rp sections one for the medieval one and one for the sci-fi one?
oh wait I found out why. We were commenting on different posts on here. Maybe it'll just be best to start a conversation? May be easier to keep track of.