I’d recommend wholeheartedly that you play the original HL - if for no other reason than to use as comparison between it and BM. It’ll be your yardstick to see how much more awesome the mod is!
But seriously, it WOULD be interesting for comparison. If there’s a part you didn’t like in the original, you could see how the BM team has improved on it; if there’s an awesome scripted sequence or fight, you could better realize how much more awesome it’ll be in BM. Or you could simply compare the level layouts and see BM’s interpretation on how this level should go.
It’s also a ton of fun, and will give you some of the best nostalgia ever. To this day, if I hear a computer-generated voice, I feel like I’m in Black Mesa ('s why I love going to the airport.) As far as the graphics go, I know they’re not exactly “current,” but I think they have an incredible charm to them. To see the incredible things that this team did with such a - by our standard - primitive engine is just amazing. That could be the nostalgia talking, though.
Well you’ve got my vote.