Lugia is my favourite.
Though isnt Sudowoodo is a special pokemon?
Lugia, because it is one of the most coolest legendaries they ever created.
The Red Gyarados because for one it's a shiny and it will be pretty epic to have in WiFi battles if they keep it in the remake.
And...Raikou, one of the coolest Legedary Beast Pokémon of the three, and plus it is an Electric Type which is a plus for me.
Out of the three, Raikou takes the win for me.
Also, how come Lapras was added in? x__x
inside the Union Cave , you can Find a Lonesome Lapras Sprite , it says that it appears in a Specific day. I dunno about this thing but ive heard that its a Special Pokemon. check out Serebii Dude :D