I think the best way to experience the original Half Life, is just to jump into Black Mesa, it's an awesome re-engineering of the game, it's free, and it sets you up for HL2 and HL3.
I'm glad, not so much because of HL3, I've been waiting for years, used to waiting for it and just kept thinking that the engine could do with an overhaul to get the most from what HL3 should be. I can be patient now, with high hopes for what HL3 can be, and what it will do to the FPS genre.
Besides, I was pretty disapointed with Ep.1, Ep2 was pretty good, I'd much rather see HL3 than Ep.3 - start fresh with some new tech and see how much ass can be kicked with it.