Well, I enjoyed stuff like Jack and the Beanstalk and The Last Unicorn, but I tried watching the Wolverine and Iron Man ones and couldn't make it through one episode. Probably cuz of my comic fanboyishness but still.
They were American productions from Rankin and Bass, who were actually really good for their time. They had a cartoon show that was shown once a week over here that I used to tune-in for every week. The cartoons were usually folk tales that were in danger of being forgotten due to the increasing number of television baby-sitters in use.
Generally the quality of the animation was above that of Hanna Barbara or Warner Bros. with their movie length offerings being wonderfully animated and produced.
Marvel comics were never too deep and quite pulpy and formulaic, so the conversion to animated cartoon was never going to ignite the world outside of the under 10's and fanboy realm. Not to mention that they are now owned by Disney, so think TMNT after they were bought by Archie Comics....actually most only know that incarnation so disregard.