The first pegasus pony that came out for the G3 line was Star Catcher, she's white with big blue fabric wings, you can't miss her. She came out in 2004. Baby Honolu-loo, the only pegasus baby (although there was a 'little sister' in later years), came out in 2005 with the Butterfly Island Playset.
In 2005 we also got our first pegasi singles released. First Cloud Climber and Coconut Grove (scented). Then later on Island Delight and Thistle Whistle (scented).
Then in 2006 there were a group of other regular single pegasi released. Royal Rose, Silver Glow, Morning Monarch, Twirlerina, Twinkle Bloom, Daisy May. The last two Twilight Pink and Windy Wisp, were late 2006 - early 2007.
I think that's about it for the G3 pegasus line.
ETA: Oh, wait, there were a couple more. 2007 had singles Pearly Pie and Aurora Mist. And there was a "big sister and little sister" pack in 2006 named Tira-Mi-Su and Mochonut. Also a holiday pony in 2007 named Snow 'El. I think that's all of them.