I really have mixed feelings about i looking back on it with a fresh, detached perspective compared to a decade ago (which btw I can't freaking believe it's been that long, how time flies)..
It was a great console with and exciting concept overall. I loved the 3D motion of the controller. I remember playing Wii Tennis with my cousin on launch day and it felt like the first time playing video games all over again. I didn't really see it as a "gimmick" like many, but more like an evolutionary step like the rumble and trigger buttons. I also didn't think it was necessary to force motion into every game like Nintendo and many third parties apparently felt the need to do. Use it when it compliments the game and that's it. Especially nowadays, I view the motion thing as more of an evolutionary step or gameplay enhancement, rather than a earth-shattering revolutionary gaming invention.
As far as its success - I still view largely reject the notion of it being a result of the "motion control fad" or "teh cazual gamez!" as many core gamers resorted to as an excuse for its sales explosion. After all, some of its most successful games used motion control mimimally or not at all (Smash Brothers, anyone?) Rather, I viewed it more as a response to the sort of simplification of games that had gotten increasingly complex and more niche in their appeal, allowing it to appeal to a mass audience who could wrap their head around merely waving a controller around in Just Dance or running and jumping from left to right in Mario. There was also the key factor in the overall strength of the library, maybe not so much from its QUALITY per-capita but from the sheer QUANTITY of games. It had such a diverse lineup that no matter what your gaming tastes, chances are there were at least of handful of Wii games for you.
The library was a complete mixed bag. A ton of shovelware by third parties who didn't "get it" but I can't fault them too much on that as even Nintendo didn't seem to get their own console judging from some of the later Wii games and the Wii U flop that followed.. But like the PS2, the sheer quantity of the library meant there were plenty of very good games, though it was sort of lacking in the "OMG AMAZINGLY EPIC" games department.
Though I feel like my Wii hype was something of a short burn, much like its sales curve itself funny enough. It quickly went from total and utter love and excitment, to "just alright" to "meh" within a few years. Now I mainly only use my Wii for virtual console. Overall it was an innovative console and a refreshing left turn from the AAA stuff on PS360 with mega-horsepower and complex gameplay.