Here's a guide of all the Scooby-Doo Christmas and Winter themed games on the Internet:
1. Scooby-Doo: Big Air Snow Show
Help Shaggy and Scooby snowboard on a ramp. Try to jump higher each time, if you don't jump as high as you did on the last jump, you lose! You can play as either Scooby or Shaggy (I prefer Shaggy, because he's a little easier to maneuver)
Overall, a pretty fun game, but not a lot of skill is required. A good game to pass the time if you're bored.
2. Scooby-Doo: Frozen Frights
A very slow game, but it requires slightly more skill (mainly through hand-eye coordination) than Big Air Snow Show.
Basically, you play as Scooby, and try to avoid various obstacles coming at you while you are trying to find Shaggy.
3. Haunts for the Holidays
This game is more exciting, one of my favorite Scooby games. It has a lot more of a plot line than the other ones. The game is broken up into 3 parts. Strangely, the first one is impossibly hard, while the other two are somewhat easier. Since this game has more to it, I'll do a short little walkthrough. Basically, the first part of the game is just a video setting up what's going to happen. Shaggy and Scooby are visiting a production of A Christmas Carol (which is why I like this one so much, it's about as close to A Scooby Christmas Carol as we get, which anyone who reads my forum will know I'm dying to have this happen). Anyways, one of the ghosts of Christmas (present) comes to life and steals the queen's crown. Shaggy and Scooby attempt to look for clues, and get locked in a room full of food. And that's where you come in, you as the player, have to move Shaggy and Scooby around 5 rooms full of food, avoiding over half the floor tiles because they have rotten food, the tiles are broken, etc., etc. If this wasn't hard enough, the game is timed for 1 minute to get across the level, making it nearly impossible. After losing and restarting the game several times (which is pretty much inevitable in this part), you will probably finally make it through the first level of part 1. If you haven't quit yet out of frustration (this isn't just me, many Scooby fans have expressed frustration with how hard they made the game), you'll move on and find yourself on the theater's catwalk. If you're not frustrated already, you'll find yourself having to maneuver around the catwalk, with one wrong move making you lose the game and (ugh!) start all over. After breaking your previous computer out of frustration, and spending multiple weeks trying to figure out how in the heck you win this game, you eventually make it to the end. This may seem like an exaggeration, but really, it is quite frustrating.
Before I go any further, you're probably confused about why I said I liked it, and then said it was agonizing. To clarify, the first part really is a pain in the neck but overall, the next two parts sort of make up for the bad first part.
Anyways, now on to Part 2. This part gets better, it begins where you are being chased by the ghost of Christmas Past and are now trying to hide in a dressing room. You have to dress Shaggy and Scooby up so the ghost won't notice them, and try to do it within 1 minute before the ghost comes in the room. This part isn't necessarily hard, but it is a little bit challenging within the time constraint. Afterwards, when the ghost finds them, you have to hide in the camera room, trying to repeat after a recording machine and remember the order the things were in. (this part may seem confusing but you'll get it once you play the game).
Part 3 is slightly better. You have to try to row your gondola to the end of the river, trying to avoid the ghost of Christmas Future, who is chasing you. This is probably the easiest, but longest part of the game. Basically, a "survival" part, no skill required. As long as you can stay away from the ghost and avoid the obstacles, there is no possible way to lose. The next part is slightly harder, you have to try to make it through the haunted 3 rooms, while avoiding bats and the ghost of Christmas Future. Once you get through the first two rooms, your goal is to then solve the mystery introduced in the first part, trying to find the crown. After you find the crown, you unmask the ghost. I won't ruin the identity for you, but the end is slightly confusing, apparently the person behind the ghost of Christmas Future was behind the other two ghost costumes, but it is not explained well.
Overall, this is my second (third if you count the deleted Crystal Cove Online) favorite Scooby game, because even though it is hard, I actually like this because I feel many of the Scooby internet games have the sort of "simplicity" because the game developers want to make it easy for the kids who may be playing this game as well, but I feel this is a great example of a game that remained unaffected from their "kid-level easiness" standard.
I've passed all of the levels, including the nearly impossible 1st part of this game.
Thanks to those who have read this far, I realize that this was a very long blog post.