Even though I love the original film, I never really seen this sequel. And I think there's a reason why...
While the original piece is an all-time classic, Winter Wonderland is more of a bad idea that didn't flop very hard. It's not exactly bad, but it has almost no charm, and seems like a forced sequel.
The plot of the special has Frosty the Snowman coming back to his hometown. He got lonely up in the North Pole, and when he returns he gets lonely after nightfall. So they make him a snow-wife, and he is happy..or something. I'm not exactly approving arranged snow-marriages.
The specials villain is Jack Frost, who is jealous of Frosty's fame. Besides causing some minor trouble, he becomes one of the worst bad guys in cartoon history. I've never seen an antagonist give-up so easily. Winter Wonderland may not be unwatchable, but they should have given the sequel more time, because the plot is rather wishy-washy.