If you're going to play any one Spyro, play Year of the Dragon (the third game).
If you're going to play any one Jak and Daxter, play Jak 2 (Jak 3 is better but unlike the first plot elements from the second are important for the sequel. The only thing important from the first game to the second is introducing the characters and what happens in the super special video you get for 100%-ing the game).