The game's best flyers are Crobat and Skarmory.
Getting a Zubat from the beginning is easy, and it has some good type coverage in its attacks with Leech Life, Bite, Fly, Poison Fang, etc.
Skarmory is only received in SS, and late-game, but if you can find a way to trade one, then it's a great asset to your team! It has incredibly solid Defense, and has a solid Attack and Speed stat so it can hit back at a decent rate.
Since you're playing HG, I'd recommend not going through the trouble of Skarmory, and getting Crobat. It's a very fast Pokemon that learns some cool moves and has a surprisingly good bulk. :)