That's what I figured, but I didn't want to get into it with someone that doesn't read comics, nor do I, and I think I understand where he was coming from when he said it.
Could you give me an example of a Marvel hero that is more powerful than him though?
Depends what you mean by "more powerful."
"King Thor" when he had the full power of the Odinforce was more powerful than the hulk in just about every way you can think of. Had crazy time powers, Vaporized Cap's shield (in an alternate future), Killed the destroyer in one shot, the whole 9. He's been powered down since then though- it's hard to write stories with someone this broken. Odin and Zeus typically operate at this level, but aren't really "heroes" in the traditional sense.
Gladiator is as powerful as he thinks he is (yes, really) and at his best has destroyed planets in a single hit, outrun supernovas, and torn stars apart. Shake his confidence and his power goes down though. I'm not sure he really counts as a "hero" though- he's not bad, but not necessarily good either.
Adam warlock usually runs around with the soul gem- he's fairly strong without it, but with it he can just steal an opponent's soul and permanently imprison it in the gem.
The Surfer MAY be more powerful than the hulk, but his power level depends on how much Galactus gives him. There really isn't an ability he doesn't have (Surfer has absorbed the power of entire suns, evolved a planet to death, thrown opponents to the end of time to get rid of them, and has matter manipulation that makes Dr. Manhattan look like a rank amateur), and the power cosmic is virtually inexhaustible- When he's not actively acting as Galactus' herald, he's a lot weaker.
Quasar is another cosmic hero that's best defined as a green lantern whose abilities don't depend on willpower. The power source of the bands is infinite, and he can make whatever he thinks of, operate at warp speeds, control all known forms of energy, blast things to atoms, etc. He's been known to just dump particularly troublesome opponents into the "quantum zone" where his energy comes from from time to time.
Thanos is more powerful than the hulk is- full stop. This is explained away as being connected to an infinite power source of some kind. A "regular" Thanos (without any infinity gems) KO'ed an enraged, power gem equipped(!) Thor then immediately fought Odin to a Standstill. He's not a hero by any means, though marvel has a habit of writing him as an anti-hero (or at least, not a villain) from time to time.
Molecule Man was probably the most powerful person in existence- he could do literally anything. Against him hulk would be vaporized, turned into a plant, etc etc. Started out as a villain, was eventually written into an anti-hero, then became deranged before sentry killed him.
Dr. Strange's power is also infinite, for all practical purposes. At his best he's defeated cosmic entities like the in-betweener with infinite power, countered the infinity gems one by one, and merged himself with eternity, becoming the avatar of all that is. Strange's power set varies so wildly though that it's basically up to the writer as to how strong he is. At the moment I don't think he's sorceror supreme, so he's weaker than his "classic" incarnation.
There's a few Omega Level mutants with "incalculable" power levels- "X man" is probably the strongest of these. At his most powerful his strength was comparable to the Phoenix Force, but i'm pretty sure he's been powered down since coming back from the dead.
Villains are a lot easier to find than heroes operating on this level though- since ludicrously powerful heroes are difficult to write interesting stories about.