Do people forget Playstation also released an exclusive Iron Man game ? That doesn't mean they own the rights.
I think there's a confusion here over ownerships of rights, and licensing of rights.
Nobody is saying Sony outright owns the rights in the game space.
There's the suggestion that Sony obtained the license to those rights. As long as that contract is in term, Sony may well have say over the IP's use within the parameters specified in those contracts. While the contract is in term, 'they have those rights'.
I mean - in the case of Spiderman for example - do we really think Sony licensed the rights for that game without some exclusivity to that use? If they didn't, what would stop Marvel licensing the rights to every other pub to make spiderman games, and devalue Sony's investment potentially?
The question becomes, what the parameters of the exclusivity are. Is it total, is it partial, where the lines are. Again, per Amos, in the context of this game, it seems it overlapped on Sony's license.
Ditto - by the way, and I think as outlined/suggested by another poster above - their contract for Iron Man may well grant similar exclusive rights in specified contexts.