Doesn't Half-Life 3 already exist?

[Souplex]

SHEPARD

*Shephard

It's taken the 17 years to finish a game that wasn't terribly good to begin with.
Duke Nukem was comparably mediocre, and that only took 12 years.

Maths doesn't check out. for Half-Life to have taken 17 years, you must be counting from the first game (1998) to now[footnote]HL1 came out in November, so it's not been 18 years just yet[/footnote]. If do the same with Duke Nukem, you'd get 20 years - 1991-2011.

I don't know how to even get 12 years for Duke Nukem, as the last entry - Duke Nukem Forever was announced in 1997 and came out in 2011 which makes a total of 14 years.

At any rate, even if you did mean that, then that's counting from the (almost) the last entry. If you do the same with Half-Life, you'd get 9 years - HLE2 came out in 2007.

If you were to count the time since HL2 was released until now, then that is (almost) 12 years.

Whatever it is, your maths is wrong.

My memory was wrong on DNF.
Half Life 1 released in 98. The last 6th of Half Life 2 still isn't out yet.
I don't know exactly when development started, but I'm fairly certain it was shortly after the release of 1.