A while back, I traded for a VHS compilation of Hanna-Barbera's 2 Legends of the Superheroes specials, which aired on consecutive weeks in the winter of 1979 on NBC, rather than on ABC, home of Super Friends. As you might expect, Legends was routed in the ratings both nights.
I missed out on the first episode, "The Challenge" the first time around, so I finally took a look when I acquired the tape. I don't know how much H-B and/or NBC shelled out to Adam West & Burt Ward to reprise as Batman & Robin one more time (or to Emmy winner Frank Gorshin to be Riddler for the first time in 11 years), but this wasn't much to write home about at all. Barryfreiman uploaded the opening to "The Challenge":
It wasn't exactly the Justice League vs. the Legion of Doom as that storyline was playing out on Saturdays on Challenge of the Super Friends, though members of both teams were represented here. The producers thought they were being clever casting comic Charlie Callas (ex-Switch) as Sinestro, but Solomon Grundy (Mickey Morton) was presented as a total tool, rather than the menace he really was. Oh, please, give me a break!
A week or so later, in a parody of Dean Martin's weekly Celebrity Roast series, they somehow got the heroes together for a roast, MC'd by Ed McMahon (The Tonight Show). Unfortunately, the clips that are available cannot be posted because the embedding codes were disabled, probably to avoid total embarassment.
Thankfully, WB hasn't seen fit to release this on DVD yet, but I'd not be surprised if the morons at [adult swim] got their hands on it......