All any dev has to do is just:
>look at the original games and A Heroes Tail which makes the levels bigger, adds a shop for items like keys or powerups, and shows environmental change based on story progression
>don't add shitty unfun minigames centered around cannons or chasing moles or boxing
>make 1 or 2 critter characters who are actually fun to play
>add puzzles or hidden level segments depending on breath abilities which also have situational usages based on enemies you fight
>rehire the dude from The Police
And theres your modern Spyro game. Its so easy it writes itself. Even