Which SciFi ttrpg has the largest player base?

[Jason]

Mongoose's 1st edition of Traveller came out in 2008. They put out the XP version of Paranoia in 2004, so it's probably Paranoia that was a hit in 2005.

In the '90s for sci-fi RPGs I was playing Traveller (MegaTraveller, TNE, T4, and GURPS Traveller), Mechwarrior, Shadowrun, Rifts (a very little), 2300 AD (a nice long campaign), Star Wars (WEG), Star Trek (Fasa), various GURPS settings (I played a dolphin in a GURPS Uplift game), Paranoia, Star Frontiers, and Cyberpunk (my group liked Shadowrun better). Twilight:2000 and Spelljammer probably don't count as sci-fi.

I bought but never played Space 1889 and TSR's Buck Rogers game too.