As a vast majority have said, it's not essential to have played Half-Life to enjoy Half-Life 2 as a game. However, to understand certain aspects of the story, characters actions, and the "inside" jokes you'd have to play the original. It would give you a sense of continuity as well besides being one of the greatest games ever designed.
Also, gabemorr, I honestly doubt it'll look better than Episode 1. In fact, I doubt Black Mesa: Source will look much better than Half-Life 2. It's been in development for quite a while now and does not use any of the update SDK components as far as the Source Engine goes.
And, to CTU_Agent 24, Half-Life did have a lot of story to it, it just wasn't spoon fed to you mindlessly in cut-scenes as many games do now adays.