Spyro is a much more casual experience than Mario 64 or Banjo (and definitely Crash), so you really have to look at it in an almost completely different light. On a technical level it's more polished control-wise and presentation-wise than Mario 64, but it rarely asks for some of the more outlandish feats of platforming that Mario does either. It's basically a pure collectathon at its core, with occasional flight levels and unmarked jump/charge challenges inside of levels to test your handle of the controls. Outside of how some of its gems are hidden, the game's other big strength is the atmosphere it sets for each stage through its visuals, music, and enemy designs.
The second a third games shake up the formula a lot with more mission-based structures to getting their story collectibles (Talismans/Eggs), as well as the introduction of citizens in each level giving each stage a little storyline behind it There's an added difficulty with certain missions as they give a lot of variety with time-based, escort, memory, flight, character-based, sport, or other types of challenges. The main objectives in these stages still play out like Spyro 1 but there's a bit more meat in how much there is to accomplish in any one level outside of getting the main plot macguffins.
Personally I still think Spyro trounces Mario 64 soundly when it comes to presentation and overall pacing and flow, but you're really getting two different things when deciding to play one or the other in terms of gameplay. If you're not a fan of the aesthetic or collecting for collecting's sake then you may find at least Spyro 1 boring or dull, while on the same token I think it's easy for people to see Mario 64 as clumsy in a lot of respects and a big time-waster in how it separated missions (a problem that admittedly and unfortunately persisted through Galaxy 2).