#10 - Spyro: Gateway to Glimmer (Kudos to S.Peelman for guessing this and also a little credit to Brendude)
Spyro 2 was always the dark horse of the series for me. Trapped between the "I fell in love with it" first game and the "this is everything that's right with gaming" sequel, I never quite gave it the credit it deserved until my most recent playthrough when I realised it perfectly laid the foundation for the third game and introduced so many different elements I liked (returning characters; a plot; mini-games; quests) about the series.
Spyro 2 followed Spyro in his adventure through Glimmer and introduced many recurring characters who ultimately made the series so special to me - Elora; the Professor; Hunter being the main culprits, but Moneybags absolutely stealing the show. Seriously, as a child I would always reject whatever he was offering just to see what insult he would fling my way as a result. Always amusing.
The levels themselves evolved immensely over the first game, too. Each level had a different set of characters with tasks for you to do to earn their talisman, and the themes were diverse - Tiki men; Glimmer Dogs; underwater Seals etc. There's even the foundation for Ratchet & Clank found in the "Metropolis" level which I found hugely interesting to replay recently.
The gameplay holds up as well as ever, too. Collecting gems has never been this much fun.
And of course, the soundtrack is absolutely top notch. I don't understand how Stewart Copeland managed to create so many timeless, addictive pieces over the course of 3 games; each maintaining a distinct "Spyro" sound through the instruments used. Really, they're fantastic, and 2 is no expection.