It seems like I've been watching Lost forever (even though it is only six years) and it is hard to imagine TV after 2010 when Lost is finished.
The thing about Lost is there is always something more. The pieces of the jigsaw go all the way back to the first episode - and we're all still trying to figure it out. You can watch episodes time and time again trying to see if you missed a vital clue the first time round.
The only bad thing about Lost is that if you miss an episode you are pretty much done for... nothing much will make sense from there-on in.
Did they invent internet/interactive/viral TV? It seems like it. All those little 'extra' bits to help figure out the pieces of the puzzle with the Dharma Initiative and all.
If you missed the first five years - wait until the last season is over, then go out and buy the DVD and watch the lot in your own time - you won't be disappointed.
10/10