Nonsense. Penelo was cute and mature, unlike the usual Genki Girl Squenix puts into its games.
Lol? Although there is always one Genki girl in FF games (see Rikku, Selphie, Yuffie etc), you'd be wrong to place every FF female protagonist into it.
Compare Penelo to Aerith. Although Aerith may have been a mary-sue in role, her courage, maturity and general intelligence are far greater than what Penelo posesses.
Penelo was standard mary-sue in everything.
Hard done by orphaned girl and orphaned boy grow up together.
They're friends.
They get caught up in an adventure.
Their relationship eventually evolves into something more.
Both parties still don't want to admit it.
Sound familiar? OFC it does, it was actually done well by Tifa and Cloud in FF7. In fact, the only role that Penelo seems to fill successfully is the one of a standard nagger.