Natural Selection 2 is a very interessting game, that represents a good blend of FPS and RTS game play.. On top of that, the community is accepting of new players and offers a friendly hand to educate those who are new.(voicechat-tipps etc)
Due to the fact that Natural Selection 2 is a hybrid of FPS and RTS game play, it allows for very competitive play in that the deciding factor of victory and defeat involves the long term decisions of a commander and/or the quick reactions and overall skill of the individual combatants (whether shooting aliens, or stalking marines). Due to this style of game play, games can very well last over an hour and yet feel very "tight" throughout the entire match.
However, as of now, there is a lack of a ranked match system. The fact that the average game easily lasts over 20 minutes, and longer games tend to last for at least an hour, a very serious deciding factor of the winner is simply how many players leave and join the game. I understand that this is not really a game breaking problem, however due to the fact that players do not have much "loyalty" to their respective team, and the fact that the average match is rather lengthy, if a number of "pro" players join or leave the match during the middle of the game, it could drastically change the fate of the match instantly. I believe that having a sort of ranked match system, like that in Counter Strike: Global Offensive, will serve a very competitive game like Natural Selection 2 justice. Having ranked matches will also remove the occasional "newb stomping" matches, where there is a skill-based team stack.
The game features asymmetrical teams with very different game play styles. This provides for a different style of FPS game play, and not the traditional shooter vs shooter like in most FPS games. I believe that because of this asymmetry, it expands the average gamer's experiences about FPS games in general. However, in Natural Selection 2, because it is also an RTS hybrid, a player could choose from essentially four game play experiences within one match alone which highly increases the game's overall learning curve. These four game play "roles" are: Marine commander, Marine player, Alien commander, and Alien player. Each type of "role" presents new strategies and information upon which the player has to know, and ultimately, having a sense of all the 4 roles is the minimum requirement for being "decent" in the game. Overall, having asymmetrical teams can interest those who are tired of the same-old shooter vs shooter, and because Natural Selection 2 is an asymmetrical FPS/RTS hybrid, such game play increases the overall learning curve to become fully understanding of every aspect, tactics and counter-tactics within the game.
Do not let the lack of a ranked match system and rather difficult learning curve stop you from playing this game however. The lack of a ranked match system simply means that Natural Selection 2 is always going to be played on a "casual" game play setting, which many FPS games have. The difficult learning curve is also easily passed if one simply spends about a good 2 hours playing in a sandbox training server by themselves, learning all of the abilities, techniques, tech-trees, map-knowledge, weapons, and life forms to get that "full" understanding of the 4 game play "roles" I mentioned earlier. Furthermore, if you still need further clarification and help, the overall community in Natural Selection 2 servers are kind, vocal, and willing to help those who ask.
Soloplayers: 60-70% fun ( or less, if you play against a pro team)
With Clan/team: 70- 85% fun