Just wondering, why did dota became famous among so many custom warcraft 3 maps?

I think it became famous because it provides many different things like back stab and team ganging on one opponent, the lvl 25 roshan , being able to help your friends on money and just being there to distract the opponent for the vital one second to let the injured escape, REAL time gaming, AIs for training, lots of items, "secret shop" and all the other strategies. It could also be that the game depends on opponent, trashing newbies to being owned, on item recipes, farming neutral creeps to game creeps, and lots more. I just like playing it because i get to play it with good friends whom will forgive me even if i became a feeder...

because everyone wants to dota!

I have thought about these things before and come out of conclusion that the whole game is very interesting and will not let you get bores so easily. The wide variety of items, skills, spells and other interesting events makes it more enjoying to play. You can also choose more than 60 heroes to play with. That makes it a better game than others. What more interesting is that you play the game with other people too. You are competing witht the opposite side while you need to work together with your teammates. That make the game more interactive and fun.

i think that because they are one of the first that offer a map with playable hero with all the accessory. most of other custom map comes after dota gained popularity.

I believe is the constant deveplopment over the years. New heto, items and skills were created to make the game more balance and interesting. Besides, as others mention, there are many things to play in the game eg. skills, magic, roles to play and etc.

I believe it has become so successful is due to the fact that it is a RPG, meaning you can really feel that you are the hero that you are playing, isnt it?