It's interesting isn't it?
It's a testament to the oldness feeling and it's very real.
It feels like just yesterday it was Sonic's 10th Anniversary, celebrating with Sonic Adventure 2. I remember getting that along with the collector's edition which had that nifty coin. (Unfortunately now I can't find it).
We then celebrated Sonic's 15th anniversary with Sonic 06. AHEM, moving on...
For the 20th anniversary we got a treat with Sonic Generations.
Now here we are with today being Sonic's 25th anniversary. We don't have a game announcement yet but that's expected to be next month. I think everyone is in agreement that Sega should in no way rush the development of this game. You may be asking however, did Sega drop us anything? There is this nifty retrospective they posted on their youtube found below.