Old Sonic > New Sonic (2005-present) 

Old Sonic < New Sonic (1998-2004)

Old Sonic is better in the old times with the new one since 2008 because Old Sonic was really, really fun. Now the new ones are so freakin' easy for god-for-saken, I can complete it in 10 minutes. (Except Sonic Unleashed)

New Sonic in 1998 was better becuase SA1-2 made me addicted, I played for 4 hours in my Sega Dreamcast (my friend gave it to me when I was 8) and the Advance games are ENJOYABLE. 

- Loopa23

I don't notice a difference.

- Road Runner1