re: What made "Lost" so captivating?

I think lost was just unlike anything we'd ever seen before. It was twin peaks, x files, twilight zone and castaway all rolled into one beautifully packaged product.
Ultimately the scope became a little to big for itself at times but it is still by far my favorite show. Here's why:

In a time where everyone was dumbing down television Lost flipped the world upside down. Deep characters whose past, present and future all intertwined like a giant spider web forced viewers to really pay attention and thus becoming invested in characters they related to.

The many mysteries of the show. Between the crash, smoke monster, the hatch, the others, polar bears, dharma, Jacob/mib, whispers, Hurley bird, the statue, the numbers and just the island itself, there was always something to keep everybody guessing. Some (like myself) feel they explained too much and others too little. Either way, people really cared.

The island cinematography was pretty great. Especially in the first few seasons. Plus the incredible MG score (life and death still gets me).

Probably most importantly lost created an enormous community of fans. From twitter to Facebook to lostpedia to podcasts to thousands of viewing parties around the world, lost was what everybody was talking about.