Mister mxyzptlk!
C'mon.
Guy Gardner would announce open bar at Warriors (domestic beer only) and talk crap till the wee hours.
"My name is Wally West. I'm the fastest man alive!"
I'll try being nicer if you try being smarter.
Diana is up there, though I think she'd shine brightest if her Amazon sisters could come through. Bull-leaping, javelin contests, Dionysian dancing, an abundance of music and wine and fruit.
Hal is definitely a party guy, but I don't see him hosting a particularly good party. He'd only have beer and food he likes in an unimaginitive, basic space.
Agree with those saying Vixen's Gala would be awesome.
I'm having fun imagining what the heroes would be doing at this party. The Titans are probably loving it the most, playing games and such. If Barry's there he's drinking quietly at the edge of the group, and later on starts to chew someone's ear off about a case he's working on. Wally is full on, running around and making sure there's enough of everything. Aquaman and Hawkman are probably stoically drinking, not socializing much until they get roped into a contest of some sort. J'onn is pleasantly people-watching and absorbing the good vibes. I can see Vixen, Hawkgirl/woman, Zatanna, Black Canary all tearing up the dancefloor. Clark is bouncing around making small-talk, and Bruce is constantly surveying the scene for when something goes wrong.
It already happened in Metal at Wayne Manor so that was my first choice as long as everyone can be discreet.
Paradise Island is welcoming but I don't get the impression it's that welcoming. Though maybe that's the 10+ years distance from Perez era talking. Depend on who's coming I guess.
Oa is the largest and they've hosted various diplomats, so it's convenient if they haven't gone home to Earth yet. As long as the Guardians are not being a stinker. So I personally prefer Mogo.
The correct answer is Cat Grant.
My choice is definitely Governor Jeremy Horton (A.K.A. Hard-Drive):
Last Read: Aquaman & The Flash: Voidsong
Monthly Pull List: Birds of Prey, Daredevil, Geiger, Green Arrow, Justice Ducks, Justice Society of America, Negaduck, Nightwing, Phantom Road, Shazam!, Space Ghost, Suicide Squad: Dream Team, Thundercats, Titans
Superman
Doctor Strange: "You are the right person to replace Logan."
X-23: "I know there are people who disapprove... Guys on the Internet mainly."
(All-New Wolverine #4)