Fantastic Four (Stan Lee) vs X-Men (Claremont 5)

Well, Stan Lee unfortunately wrote Invisible Woman as little more then a damsal in distress who was only useful in getting captured so the other 3 could rescue her. That automatically takes her out of the fight as a less-then-useful member, making it 3-vs.-5.

Colossus and Wolverine could double-team Thing. Either one of them would be a decent fight for Thing, but both together over-whelm him. Storm and Torch would be a good fight that I think she could actually win the majority against on her own, here she just has to keep him at bay long enough for Cyclops to take him down with a well-placed optic blast, which shouldn't take to long.

This leaves only Reed. Don't want to underestimate Reed as Stan tended to write Reed as a crazy deus-machina character that would always whip up something crazy to save the day. That could happen here, but I say that's not likely given that this is a random.

So basically, I say the X-Men team win 8 or 9/10, with the odd 1 or 2 for when Reed is able to whip together an I-win device from discarded trash before the X-Men are able to get to him.

Yeah...

I've read Stan Lee's run on Spider-Man and although I realize the the time period in which they were written was very different, today they come off as pretty sexist lol.

X-men FTW if this is a random encounter. Storm and Cyclops, even during this time, were promising tacticians and this team has enough raw power/versatility to take the majority.

Storm creates a pea soup fog around the team hendering the visibility. Nightcrawler then BFRs Sue taking her out of the game. Storm can snuff out HT's flames with her winds like she has done before taking him out, leaving Ben and Reed to be taken out by the rest of the team.

Agreed on @roddy010 and @moonchilde. X-Men for the win.