Was watching a friend play this one this week and it just gave me the itch to play it once again.
Honestly, this one just gets better each time I play it. While I do find S3&K to be the gold standard for Sonic games, this one brings so much aesthetic to the franchise, both visually and soundtrack-wise, that it just warms my heart.
Also, the 2011 port is AMAZING. Some really good quality of life changes to the game that make it the best possible way to play this one (unless you own Origins...)