I absolutely loved both games. I played the original on Dreamcast and then Shenmue 2 on Dreamcast as well. The first I played with the English version, second with the English sub and Japanese voice acting.
Once I completed the first game, leaving on the boat, I was really excited to see where the story would take Ryo, so I jumped into Shenmue 2 and it hooked me. For me, the thing that drives me most to play games is having the story unfold, and that's what Shenmue 2 did. Shenmue 2 definitely felt different than the first, but to me that was part of Ryo's story. He was no longer home, he was on a journey, and that is what Shenmue in it's entirety is. No longer do you stay in one locale, but you traverse through many regions. No longer do you have one place to call home and sleep, you actually have no home but multiple places to sleep. It's all part of Ryo's journey, and I guarantee that if you stick with Shenmue 2, you will be glad you did.
If I had to choose between 1 and 2, I would definitely take 2 because of the different locations, how much of the story unfolds, and the very different moods and atmospheres the entirety of the game encompasses.
Let's hope Shenmue 3 pops up soon.