Half life 1, 2… hm.
Ok we’ll make three HL2 episodes to follow that up.
Ep I. Ep II. Uhhhh… and let’s stop there, just like forever I guess.
Portal 1. Portal 2.
Left4dead. L4D2.
Team Fortress. TF2.
Counterstrike. CS2. Oh shit we’re releasing a third one, we might have to use the number three finally, oh no… I’ve got it: CS:Go!
Regardless, point stands: they hate the number 3.
Then again, all kinds of companies take liberties with naming including numbers. Look at Windows 7 (12th major release), Windows 10 (successor to Windows 8), the game Battlefield 2 (third in the series), Battlefield 3 (three games after BF2), Battlefield 1 (after the release of BF4), etc.