About Arbok.....it doesn't learn as many dragon moves.....
Sceptile's a grass-type.......we have yet to have a grass dragon, and it has few similarities to other dragons (Milotic would get nowhere without Gyarados).
Tyranitar's a dragon in my opinion, as he's a dinosaur-ish pokémon, and aren't dragons meant to be left-over dinosaurs with superpowers? (Don't go all angry, but that's a general stereotype of dragons).
Still, like I said, you can get an argument for/against a pokemon, and just write it up, then pm/vm it to me, and when we start, I'll put it up for people to see, alongside the opposing argument (i.e. for Milotic and against Milotic).
Good luck with your list, Tkallab!
And I know dragon moves can't really be counted (lol, Mew's now a dragon, right? I think it may even be able to learn Draco Meteor....), as pokémon like Arcanine and Kangaskhan learn them by tm and level-up, but still, if it doesn't get any, it can't be a dragon....