The 64 Smash was kind of on the bad side, even for N64 standards. Compare the models of characters like Mario and Link, to how they looked in their respective games (Super Mario 64 and OoT in this case) and they're miles behind, they're a lot less detailed and more polygonal, and that's pretty weird, as fighting games, being more simple than 3D adventures with relatively open worlds, usually can go all the way when it comes to graphics.
Then came Melee. As an early Gamecube title, Melee's graphics were almost mindblowing, it held up pretty well even late into it's lifetime, sure you might not think the same now that you've seen today's graphics, but back then? Characters looked like they were perfectly rounded, with all the detail they'd ever need to have. It was hard to imagine how graphics could get any better than that.
Brawl pushed it further, lots of people now say it doesn't look
better, and I don't know if it's superior from a technical perspective, but it certainly looked far more impressive than Melee did on what was then though to be hardware with the exact same limits as the Gamecube, just look at the reveal trailer when they show the characters changing, the jump was
huge. Looking at games on other consoles and the PC, it's graphics were basically nothing, but as a Wii game, it looked pretty darn good.
You can't say the graphics look good because of the colors...
Yes, you can.
I honestly always disagreed with the whole deal about graphics refering only to the technical standpoint. (because that's actually not what it means, the word has existed long before video games were a thing.)
If a game looks good, it has good graphics.
If game A looks better than game B, then game A has better graphics than game B.