First encounter actually nullifies a typical Iron Man fight. Which is: a) detection & data gathering b) test c) upgrade to match. Iron Man has the tools to survive first encounter, but first encounter is needed than he needs to rely on his onboard computer and resources at hand, which I say is still very significant. Satellites, arsenals, holo-emitters, temporal stealth capability, other iron suits will come in play. Except the top 25% of GL, Iron Man will still eek out a win by his wits in first encounter only.
Also I forgot to say, Iron Man's data gathering is one of the best in the business, far surpassing Batman. The man has a knack to know the opponent's achilles heel thanks to his onboard CPU.