The problem with a question like this is context. After the NES, Nintendo suffered from intense competition with every system they produced. Strangely, it seemed that on the hardware side, Nintendo was more concerned with whether their first party titles could be done well on it (or at least better than their last generation hardware,) without an awful lot of regard to what 3rd parties might wish to do. The type of titles Nintendo specialized in, really weren't the most demanding. The mini-CD format of the Gamecube seems to underscore this ideology. Unfortunately, this put Nintendo at the peak of the curve for what was possible on their systems, perhaps by design. Knowing this, the 3rd party developers almost always put more effort into the other systems, and left Nintendo with sometimes shoddy, scaled down versions of games. Without robust 3rd party support, no system can compete at the same level as others in the marketplace.
Personally, I really liked the N64. The games from RARE and Nintendo especially, were very well done, and great fun to play. The snowboarding and jet ski games were two which stand out, and which I have never found an equal experience with on any other console to this day. Call me strange, but fancy graphics and a zillion options don't make gameplay better for me. But graphic capabilities became a system benchmark for the masses, and Nintendo didn't really keep up (and really, still hasn't.)
The Wii wasn't a bad system at all. But the marketing and the hype left high expectations to which it could never rise to meet. The limitations on 3rd party developers hurt it as well. It made Nintendo a lot of cash, but it damaged their reputation in the process. With higher-end competition from Sony and MS in the marketplace, a huge chunk of consumers will likely never risk purchasing another Nintendo console, unless their needs are primarily those of it being low-cost and aimed at the younger gaming set.
The only really "bad" system Nintendo ever produced was the Virtual Boy. Every other system was good, it just wasn't as good (with the exception of the NES), IMHO, as other options available (or emerging) at the times of their release.