It was called Super Mario War, and it's pretty awesome if you ask me. The only downside is that the multiplayer is local play only, but there are bots that are fairly decent. They only get stuck every now and then, and since the game is pretty much just a quick pick-up-and-play kind of thing, it's not a huge issue. Local play is *very* fun, and supports up to 4 players.
Here's a vid of their 1.8 patch stuff. You can find plenty of other videos if you search.
It used to have buttloads of custom content, but it was all unfortunately lost when their servers and whatnot went down... HOWEVER, it turns out I am the only person to have a "complete" collection of it all still backed up. It isn't actually 100% of the custom stuff, but it's a helluva lot of it... way more than anyone else in the world has been able to supply.
The game is incredibly cross-platform (though you may have to compile it yourself for that (source is here https://github.com/neagix/smw-next), or grab the Mac or Linux version https://code.google..../downloads/list), even being playable on a hacked Wii (http://wiibrew.org/w...r_Mario_War_Wii). It's also open source, comes with a level and world editor, and is very easy to add custom content to if the collection doesn't quite have what you're looking for.
So if you're interested, here's my collection of stuff. It comes with the full game (as well as the level editor) and as much custom content as there is available. Primarily: 5400+ maps, custom worlds/tours, some announcer packs, custom skins, etc. The only thing I never downloaded was custom music/sfx, but the base selection is what most people prefer to play with anyways. A word of caution: some maps will have invalid blocks (they look like pinkish/red see-through boxes). This is because I wasn't ever able to get all the necessary tilesets. It only impacts a very, very small portion of maps and they are still playable... they'll just look weird.
My "full" collection download:
The default menu controls may not be to your liking, but it's all easy to change. The default (because of my settings) are WASD to move around the menu, ENTER to select, and SPACE to randomize (only certain things work for that.. but it's great when picking a map). Map selection can be incredibly tedious due to how many there are, but you can type quickly and it'll filter through them.
If you get DLL-related errors: you just need to copy the included DLLs (msvp71.dll and msvr71.dll) to your Windows system folder (Google it if you aren't sure where they should go). For most folks this will be either "c:/windows/system32/" or "c:/windows/syswow64/". These DLLs were actually just normal Windows-distributed ones, but at one point Microsoft stopped including them.
There are also a few secret features, though I can't verify them all. Here's what their forums said about them:
Moonwalk mode: 9 fire flower kills and more than 5 noteblocks jumps
Dizzy Mode: 4 or 5 ice wand kills (possibly not correct.. other sources say: 5 kills in a row without dying by different two players, and 3 ice block kills)
Wind Mode: 2 players need to get 2 in air consecutive kills and break more than 5 bricks
Dark Mode: left, right, left, right, jump, jump (three times, very fast... so: L, R, L, R, J, J, L, R, L, R, J, J, L, R, L, R, J, J)