To the Pokemon Trainer boards: you've obviously never been in the Falcon boards. Most of them don't like to be serious (MOST, there are some intelligent people out there.) I'll answer your silly question anyway.
Squirtle: Squirtle outranges Falcon in the air and edgeguards him quite easily. Falcon, though not as swift in the air, has many more options than just FAir and BAir, as well as the ability to KO Squirtle at lower percents. Squirtle isn't really as easy as everyone here seems to think. I'd say Neutral.
Ivysaur: No doubt, Ivy's advantage. He outranges and outprioritizes Falcon and shuts down any method of approach that Falcon may have. Definite Ivy advantage.
Charizard: Charizard KOs Falcon easily, stops most of Falcon's (nonexistant) approaches with his tilts, edgeguards him easily, racks up damage quickly, and has Falcon easily succumb to Rock Smash. Charizard's advantage.