Charizard G is one of the anticipated cards of Supreme Victors and that 150-damage attack is hard to pass up such that it be seen as one of the attractions of the card (as well as the fact that it's a Charizard).
It's HP is very good for an SP Level X (along with Dialga and Palkia), resistance to fighting is welcome (although Machamp still KOs it with Take Out), the retreat cost is horrible and the weakness is bad. Come to think of it, any weakness seems to be bad in this format (Beedrill for Grass, Blaziken and Infernape for Fire, Palkia and Kingdra for Water, Luxray for Lightning, Machamp for Fighting, Gengar for Psychic, Flygon for Colorless/Dark, Dialga for Metal).
It's Poke-Power is awesome and not Power Spray-able, which is a plus. Call for Power is quite a self-centered Poke-Power which is meant to help power-up it's expensive Malevolent Fire attack. 5 Energies (or 4 with Energy Gain) for 150 is neat but at the cost of discarding all energy on Charizard (at least it's on a flip). Although there are certainly ways to ensure that you can use Malevolent Fire every turn, it is at the cost of running too many supporting (and often non-attacking) benched Pokemon. It's difficult to set-up and if you do succeed at setting up the bench, there's the risk of an opposing Water Pokemon to ruin all the work.
What makes SP great is that they are disruptive, and have cheap attacks. Charizard fits neither these descriptions and in reality, a deck centered around the card is more of a set-up deck. And just like most set-up decks, it will have a hard time to compete in the current format, and will certainly have issues with speed and consistency.
It still remains to be seen if anyone will be able to make a Charizard deck fast and consistent enough to be considered competitive. Until then, Charizard can certainly make for a fun league deck.
Modified- 5/10 (too much resources needed to set-up. Luxray can do 150 in two turns with Crobat drops and much less resources)
Limited- 3/10 (good luck powering it up here and hope you get heads on Malevolent Fire)