I never really got into the Wii's library until the beginning of 2012
I would say this has a huge impact on why you say the Wii is under-rated. Coming to it late when all of the games worth owning on the system have been released would make you think it was better than what it was, I imagine. Owning a Wii since 2006 was a totally different matter, however.
In 2006 I had
Wii Sports,
Red Steel and
The Legend of Zelda: Twilight Princess. Only
Twilight Princess was worth the money. The next major must-have game (in my eyes) was
Super Mario Galaxy which came out in 2007 along with
Metroid Prime 3: Corruption. I also bought
Resident Evil 4: Wii Edition in 2007, which was a port of the PS2 version. 2008 was the Wii's best year in my opinion, because three games worth buying were released:
Battalion Wars 2,
Super Smash Bros Brawl and
Mario Kart Wii. 2009 had
Super Mario Galaxy 2 and nothing else. 2010 had
Donkey Kong Country Returns and nothing else. 2011 had
The Legend of Zelda: Skyward Sword and nothing else.
I owned many more games for my Wii, many more indeed. Problem was none of them were anything particularly special.
Mario Strikers Charged,
MySims,
Sonic and the Secret Rings,
Big Brain Academy,
Wii Fit,
Dragonball Z: Budokai Tenkaichi 2 and
Super Paper Mario were hardly 'must-have' titles, most of them were complete turd (I'm looking at you,
Sonic). So between 2009 and 2012, there were only 3 games released on Wii that appealed to me in any way. Now, that is obviously just me and I know other people will have had a bigger list than that but even the JRPGs every bangs on about all came at the end of the Wii's life-cycle so for the majority of time owning the system, you would have had very few compelling games. What's more, almost every single game worth owning came from Nintendo and not third-parties.
No one really took advantage of the Wiimote, not even Nintendo until
Skyward Sword and the Wii's lack of power kept thrid-parties away from it. It's online showing was nothing short of abysmal and it just seemed like I was playing other consoles and never the Wii. I have got the most use out of it by playing GameCube games and that's sad.
I would say that the Wii is not under-rated, not even slightly. Aside form a handful of amazing first-party titles, the console was, for the most part (dare I say it about a beloved Nintendo product), a waste of money
O)