Chris Hardwick thinks Wonder Woman's paycheck needs to match Iron Man's ... 'cause the actress playing her is just as good as Robert Downey Jr., if not better.

We got Chris -- who's a certified comic book nerd(ist) for this kind of stuff -- and asked what sort of money Gal Gadot should negotiate for in any coming "Wonder Woman" sequels ... this after learning she earned just $300k for 3 movies each

Chris doesn't mince words -- he says she's in RDJ territory now after 'WW' killed with audiences across the world. And his suggestion is on par with RDJ's salary for at least the last few 'Iron Man' flicks.

Stepping on his metal toes?