Of the early Sonic games, Sonic CD was the best. Save feature, balanced ring/trap ratio for moderate access to Special Stages, time travel and early access to Good Future meaning extra music and stage paths, the simple Time Attack unlocks, and the overall aesthetics made it great. S3&K later marginally topped Sonic CD through the post-game backtracking/save, large special stage rings and the 50 rings it gave you afterwards, Tails and Knuckles, and the Super/Hyper forms, but that's another story.
But after a while, the stage designs got to be downers. All of the 2D Sonic games did this, but Sonic CD's level designs were even less friendly. They run you around in circles; you can't intuitively and freely cover more ground in Wacky Workbench, Stardust Speedway, and Metallic Madness. So, all of that potential extra replay value only applied to the first few zones.
But. It's all still designed in a fashion where you can mentally map the fastest route through an act, and that's far more than I can say for current level designs. ...and mechanics.
So enjoy it. Enjoy it the same way you do any old Sonic game you've beaten 100%; manically blaze through the zones and let the adrenaline rush.