the only games i didnt finish in like a day (i sometimes play all 24 hours :p) which hooked me up for quite a while was:

monster hunter freedom 2 due to its insane difficulty at first. however, i gave up after being unable to play with others.

phantasy star portable for its immense replay value as each class/race plays so diffirently from each other, also quit it after getting all the best items and being doomed to playing alone :/

wifi max = hardware

xlink kai = software

you need both to play it online, as the software just tunnels the signals through your pc and thus, simulates ad hoc.

You can use another wifi stick if you want, but make sure it supports "promiscuous" mode (which almost none do).

The singleplayer of MHF2 is great, however, you will soon be wanting to play it with others and thats why I wouldnt advice you to buy it, since there are only like 10-20 people playing it on xlink kai at times.

Monster Hunter 2nd G, on the other hand, is played but over 700 people at any time. Only be aware that MH2G is on Japanese.

Phantasy Star Portable is the best imho. You should import it, it is really not hard figuring it out. I played through the story like 3 times without being able to read a single letter in japanese nor even having played other phantasy star games. Trial and error is all you need to figure out the items, stats, etc.

It is going to be very frustrating the first few hours though.