for me, it's mainly the titles.

-there are a lot of niche-import games for it, and since development costs is cheaper for the wii compared to the other current-gen consoles, a lot of smaller studios can produce games for it. Guys like Suda51, the people at Xseed and occasionally Atlus are eager to provide the titles for it.
yeah shovelware comes with lower development costs, but it is only an issue for the less-discerning gamers (i.e clueless parents). There are tons of brilliant titles for the wii that most people give a miss for lazy-waggle-input-carnival-games.

-Backwards compatibility: I haven't had a Nintendo Console since the SNES, and with Gamecube BC, the wii has a much more expanded library, compared to the ps3 which decided to forgo BC for some retarded reason. also VC allows me to catch up on the great nintendo games I missed throughout the years.

And of course, most titles available for the ps3/360 are available on the PC. I have a decent PC running for my current gen fix.