ROTMG

Ackhually RotMG has been around since early 2010. Rob actually held an AMA on the subreddit to mark 10 years of RotMG this January.

Going off of the actual release date of the game but sure it has been around since 2010 in Alpha or whatever you want to consider it

You're probably thinking of RotMG being released on the Chrome web store, which happened during 2011. This was merely Wild Shadow offering RotMG on an alternative platform instead of a "1.0 release". The game was never in a public alpha or beta stage and was fully released as is during early 2010 as a game jam entry.