not all games work online. it depends a lot on the concept of the game.
games that were designed with online play will have elements that fits online.

keep in mind that the development cost isn't the same when you have both single and online play.
if you split your resources, the outcome will not be as good if it was focused.

then again, if the project has enough money to split between the 2, it's all the good for consumers.

personally, i prefer online play on the PC and the consoles to multiplayers offline.

 yeah, i do.  yeah, it does suck; like, i liked civ a lot, but the RTS games like age of empires give me motion sickness quite badly so even though those are the kind of games i know i would like i never ended up playing them.  i stuck to turn-based or psued turn-based games like europa universalis.

yeah, online games aren't gonna look much different.  but at least there's the extra justification to just get through it, half an hour or something for the sake of laughs.  

which is why the DS is great--all these great games in 2D!