In an effort to reconcile Audiofeil's comments with others in a productive and educational way, you can see both Mr Wonder's talent and girth in the PBS special "We Love Ella".
Coincidentally, I was listening to "If its Magic" and "As" last night on my PC based desktop system.
To my ear, those two tracks are so different, but transition from one to the next in a very beautiful and flowing way - the type of magic that you can find throughout that album even after years of listening.
Songs in the Key of Life definitely helped me to become an audiophile and learn to calibrate turntables and speaker placement. Musicquarium is also a classic. The Secret Life of Plants was also interesting, with similarly layered sounds, voices and instruments.
The earlier stuff I also like, but IMO had a grittier and less layered sound, both in terms of music and the quality of the recordings.
My vote is also in the "genius" camp.