Defenders of The Ancients 2 is a great game coming from one of the best mods available.

User Rating: 9.5 | Dota 2 PC
Valve made a great choice by making a modable standalone version of DOTA. It raised the bar for making the modding community stronger with having the game to run on the source engine and also made it "stand-alone" in one freaky way or another.
I started playing Heroes of Newerth as the first MOBA game after the Warcraft version. It was pretty close to the original and I found League of Legends lacking in community related stuff. Also it was a lot more casual for my taste. When the DOTA 2 beta came out I was so pumped to get back playing a new version with better graphics than on the Warcraft version.
I really love how Valve has implemented the steam workshop and how it grows each day. I also like that all heroes unlock at the start instead of buying each heroes like you do in other MOBAS (LoL) It makes the choice of your heroes a lot better since you can always try to counter the other teams heroes if you wish, than always playing the same hero hundreds of times before you get the runes for it and then can play it for eternity.
This is what makes DOTA 2 such a great upgrade from the mod.