Games may have 256 players online... but how many ppl can play Pikmin? If you go with the min. of 4 ppl, and they keep the maximum of 100 pikmin, that's at least 400 characters, meaning it will actually be harder on the network to process. Add the fact that these 4000 pikmin will be doin many different things at once...It will just add up to really bad lag. Unless of course, you're lucky enough to have extremely damned good net.
There's only 4 players though, the rest is just AI. The Pikmin literally just follow you and go where you order them, they're not dynamic.
They are dynamic and the things that happens in the game are physics based, Pikmin was a game based on how good the horsepower of the GC was, it originated from a demo called mario 128.
online multi player games such as FPS's only need to sync players actions and location. Every player have their own internet connection.
And if something lagged on someones end it wouldn't affect the rest off the players or the fired bullet location since a bullet is route is determined once a player hits the trigger, there are no major live calculations going on when it's in the air.
Pikmin however only have two players controlling hundreds of objects on the screen and none of these have a predetermined outcome, they bounce off walls, enemies etc. there's tons of data of their location in 3D space, that's for over a hundred objects flying about and on top off that the game have to sync collision detection, damage etc, it's probably impossible to sync given the average internet connection speed.
Imagine throwing a Pikmin only to miss the enemy because of lag.
No one here wants online for that game, there are many other games that need it and haven't gotten that treatment, this game isn't one of them. Playing against people online would just be tedious since you have no idea how good their Internet speed is. The game has online leader boards and that's all it needs.
RTS games don't have physics that needs to sync live, only estimated x and y values and other commands, as I said before Pikmins outcome isn't pre-calculated.
In StarCraft for example units move in clusters and in Pikmin all the Pikmins locations must be processed individually in a 3D space with live calculations of bouncing, falling speeds etc.
Look around the 9:10 mark in this video to see what I mean about physics.