I think it's too very different kinds of knowledge. Tony Stark's an engineering genius, but they've also hinted he's a bit clueless when it comes to other things. There's a great little bit in the first
Iron Man when it's pointed out that Tony doesn't even know his own social security number (I just did a Marvel marathon last week and watched all the films in order

).
The Riddler is brilliant, but it all seems very focused through the lens of puzzles/ riddles/ challenges. If he was a real person, there'd probably be some autism-spectrum diagnosis you could make. His knowledge base seems much wider, but he's limited by how he can use it.
I'd guess the Riddler would kick ass on
Jeopardy, but Tony would be the much more entertaining contestant.
