Clearly should of evolved to Quilava, hell they done a whole episode about it. It's one of the few things in Johto I was upset by, as Ash's team seemed very weak when Charizard and Squirtle left, and then later on Bulbasaur. Despite this, I really enjoyed all three of Ash's Johto starters having very differant personalities, like his Kanto starters.
In Johto, Ash never really had a strong powerhouse in his team, great series never the less.