There are several issues with the games popularity, I think.
#1 - There are just so many games in general, now. Players are spread thin. We may actually have more players than ever, but the actual amount of time that people spend playing paintball2 is at an all time low. I know I, personally, have a good 5-10 games I'm actively playing at any given time, which means I can only spend a little time with each.
#2 - "Oldschool"/arena type shooters just seem to struggle to keep active players in general. I don't know why, because I find them to be the most fun. The UT and Quake style of gameplay just doesn't seem to be popular anymore. Rise of the Triad 2013 just came out, and they're already down to having organized deathmatch nights, just to have enough people to play.
#3 - It takes a lot of time and dedication to become good enough for Paintball2 to really be fun. Most people aren't going to see the potential. They'll probably hop on a speed server for a bit, run around aimlessly getting killed, then uninstall, without seeing the true potential of the game.
#4 - It seems popular games these days are less about having fun core gameplay, and more about tapping into the compulsive human psyche. As much as I hate it, some players just won't keep playing a game without leveling and player progression.
There are a lot of things we can try, but I'm not really certain what, if anything, would make the game really popular. These are just speculation on my part.
Things I don't think will make much of a difference:
- Revamping the website. How many gamers really look at a game's website? What % of players do you think visit, say, the Call of Duty website? I haven't.
- Voice chat. I think most players tend to not want to talk to strangers online. If they have friends in game, they will probably use vent/teamspeak/mumble/skype/etc. with their friends.
- Purging unused accounts. Is your ability to play with the name <insert popular character name> going to make or break it for people? Would that name really be freed up if inactive accounts were removed, or would it just be immediately taken by somebody else?
- Standardizing server names (players are most likely just going to jump on whatever server has the most players).
Things that might help:
- "Quick match" (with bots, if no players are available). If players can just press 1 button and get into a game with players/bots (ideally, at their skill level), they might not be turned off by passworded servers, empty servers, high ping servers, etc.
- Stats/ranking/levels - some carrots to dangle in front of players that won't stick around without them.
- Competitive mode with lobby and built in IRC. Something more organized and connected to the community than generic pub servers, but more accessible than match server rentals.
- Improved first run/tutorial experience.
- Friends list.