Growing up, thanks mainly to animated series, Barbara Gordon was the Batgirl I grew up with. But she's much better as Oracle and Cassandra Cain was a far superior Batgirl.
I suppose Wonder Woman would also qualify. I'd read some books involving her--Kingdom Come probably the most significant--but I think my first real consistent exposure to her was through DCAU. Once I became more familiar with her in the comics, I honestly hate how she was portrayed in JLU now.
To be honest, speaking personally, I think I'm the opposite of this more often than not. I tend to mistrust first impressions and I don't hold nostalgia in high regard.