Okay, first off just hear me out before you let the flame war begin! What I am confused by is the fact that everyone thinks it is so incredibly ridiculous that it had taken 6 years, thus far, to make this game.
So lets break down how long a normal "triple A blockbuster" title with a full staff or animators, voice actors, story board artist, programmers, character artist, map artist, texture artist, managers, pr staff, advertisers, and last but not least SALARIES, take to make a game. It is not unheard of for these professional outfits to take 3-4 years to release a game!
The Black Mesa team are a small group of people that are doing everything from advertising, web design, keeping the forum updated, PR, game and level design, animation, music, voice work, and beta testing, etc. all by themselves without even the luxury of living close to one another or even having the comfort of monetary compensation.
The FINE people whom are creating Black Mesa aren't just making a quick "Half Life: Source" like port, they are completely remaking every last inch of Half Life from the ground up, in their spare time, WITHOUT getting paid for it. If anything it is costing them money to make it with all the lost time that they could have spent developing for money.
With all that being said I think a job this big with a team this small that only works on their spare time, 6... 7 years even, is really not that crazy of a time span with all things considered.