Sure, this one contains also Doom, Doom II, Doom 3 Resurrection of Evil, and The Lost Mission so there is plenty of new content for only Doom III owners ;)

Just note, that all of those games appear just as "Doom III BFG Edition" in Steam Library and you can choose which one you want to play in-game only, so you'll have 2 copies of Doom III.

Have fun :)