Again, a larger image is really necessary to be able to evaluate the card.
For the artwork, I'd say it's alright. Not my favorite gengar card of all time, not the worst. Gengar ex is probably the worst gengar for artwork, with either Sabrina's Gengar from gym challenge or dark gengar from neo destiny being the best.
6/10 for artwork.
For playability, I think it's obvious that this card is meant for the lost world stadium. It's a monster with it, but without it it's just another card, really. Lost zoning your opponent's pokemon is alright for crippling their setup/recovery, but without lost world it just doesn't instill the proper fear. I'm not sure if you'd put it into the popular gengar deck right now (vilegar), but it might be good as straight gengar with the level X and some techs.
7/10 playability without lost world.