At the time it was the other way around, with DC (and Batman specifically) being the hot IP. That's why Universal was able to get such great contract terms, Marvel was in trouble with trying to be relevant and find its way in the changing market.
Warner decided they wanted to do it themselves with their Six Flags parks and they were VERY successful. The representation in the SF parks now is not an accurate picture of what it had been under Time Warner ownership. They basically cloned everything that Universal was doing at the time and did it quite well. Successive owners of Six Flags and Warner losing their way with the DC franchises have let it all go down hill.