They're both good guys who share similar attitudes and personality so I think they'd get along (eventually), but both of them like to collect gems in their respective games so either one could easily mistake it for their own if their paths should cross. Who does it belong to though? Depends who is visiting who's game/dimension :shrug:
Spyro: Not so fast, Blue. I saw it first Sonic: Sorry, but that emerald belongs to me and it's not my fault you were too slow to pick it up Spyro: Are you color blind? That's a ruby and it's mine