Trackmania 2: Canyon: Released 14th September 2011 on Maniaplanet, 27th February 2013 on Steam.
Trackmania 2: Stadium: Released on Steam and Maniaplanet on 20th June 2013. Was in Beta since 27th February 2013. Was mostly made as fans demanded that they remake Trackmania Nations in the new Trackmania 2 Engine.
Trackmania 2: Valley: Released July 4th 2013 on Steam and Maniaplanet. Was being made around the time Mania Planet was announced, but they decided to do Canyon first. Was released around same time as Stadium 2 because they were both being develoeped at the same time and were both completed around the same time and Nadeo, the developers, did not want to hold it back for later.
Shootmania: Storm: In Alpha/Beta since July 2012, went into an Open Beta 12th February 2013, released on Maniaplanet and Steam on 10th April 2013. Was Nadeo's first attempt at a FPS.
Maniaplanet: A hub for the 'Mania Games. They expected when first talking about Maniaplanet to have 3 Trackmania 2 Environments, 3 Shootmania Environments and 3 Questmania Environments. These were expected to release 3 titles a year, but that is not real anymore as they took longer to make the games than they thought.
Also, still based more on time than collisions.
Shootmania is expected to have 2 gamemodes for free at some point and there are talks to maybe make some Trackmania 2 things free, like maybe the singleplayer as a demo or something.
I have all 4 games and I would say to hold out on buying them until maybe there is a sale or something, but I do like them.
They also might throw some 3-day codes out to peopel who have the games like they did last year for Canyon and if that happens, i'll be sure to post them here.
Also, the playerbase over all 4 games averages about 1,000-1,500 each night in total. Stats of how many players is shown here, split up by the games:
http://mania-actu.com/eng/staticpages/view/46/ManiaPlanet%20StatisticsAny more questions, just ask.