My experience with Trek newcomers is that younger males are easier to hook with DS9, older people or people who want to watch with their girlfriends are easier to hook with TNG. So I'd go with DS9, it has a lot of things in common with Battlestar Galactica which he already likes.
When I wanted to hook a friend on Stargate I started with Shades of Grey. I would start with an early episode that stands on its own, but is also one of the really good ones. Then if he likes it he'll be motivated to start at the beginning. (Ooh. THE VISITOR! Perfect intro ep.)
Or, another friend of mine who got into Trek on his own, he started by watching TNG with his girlfriend. Then when he was away from his girlfriend he powered through DS9 and said he liked it more.
But I have never met a person apart from this board who likes Voyager.