I love a lot of things so I wouldn't say that Tamagotchi is number one, although, like many of us it ranks pretty high still. My own list is something like this:
1. Dolls (I know, very surprising of me)
2. Pokemon (like EMF one of the reasons is that I've been playing this game for over 15 years now! Thats a LONG time)
3. Kirby (to the point I'm preparing to launch a 'darker and edgier' comic with personified characters based on the franchise)
4. Gravity Falls (take my love for the dark and twisted, throw in parallels to Twin Peaks that's one of my favorite shows of all times and you got yourself a recipe for success)
5. Tamagotchi (because they've stuck with me to this day, I love the characters and no matter what find them enjoyable and fun to take care of! I think that's reason enough...)