Checked, and my favorites growing up were the originals, the new scooby doo movies (my favorite was the one with Cher - I had a weird crush on her), the 13 ghosts (don't judge me), and most of the 90s and 2000s movies. I also enjoyed mystery inc a lot and shaggy and scooby doo get a clue. Each one had its charm, though.
If I HAD to pick a favorite, the movie would still be Alien Invader or Zombie Island (pic related). The show would be Mystery Inc or 13 ghosts. For me, I could watch those over and over without ever getting sick of them.
Did you like scooby doo as well?