Yeah, trying to give a fair assessment, you will probably have an overall better sound experience on an NES from a gaming perspective due to the channels and the ability to play a lot of tunes. Some C64 games had sound effects cut into one channel of the music when playing, other games had even no sound effects and all you heard was the music. The NES had a good chip, and it honestly wasn't too far behind the SID, but it was not often utilized like the SID.
One thing that makes the SID more legendary, other than the chip itself was just the circumstance of it. The commodore was about the first computer that ended up being more versatile than just blips and boops, and the chip's level of ability was honestly accidental... the video game industry was the wild west, programmers could work on what they wanted, and this new ability instantly enraptured many new programmer/musicians. C64 publishers were constantly pushing the envelope and learned how to code music exceptionally. Combine that with the fact that the commodore has extremely limited space constraints, and musicians would be making a music library of one or two songs for the entire game. These people were set out to make their opus on each game, while an NES musician may be tasked with 15 songs for a single title. I have the impression many NES musicians looked at the composing, then translated it to chip tune with the perspective more like a midi tool. SID musicians experimented with the chip in more of a jam session way and built songs around what they could invent from the chip.
So to give an example of what I mean, take a listen to Silver Surfer on the NES, the reason I chose this one is because the game was produced by Arcadia, which was formerly Mastertronic, a huge budget C64 publisher. While this game is ass, the composer here had music for at least 15 ZX and C64 games under his belt when he made this for the NES. I think you will notice there is a ton of atmosphere. There are layered, wide selections of different instruments and not only standard 8 bit blip notes, but long, varying pitch tones woven in. In short there is a lot of dimension to the sound. Not casting this on all NES games, but NES typically could be the same hook over and over and is often more memorable for well composed, tune rather than the sound squeezed out of the chip itself. Most NES 3rd party publishers jumped from Arcade to NES, and at least to me, the lack of creative chip usage is just noticeable.