Well arkham, if you were to go in timeline order it would be 3,1, then 2. In my opinion, I that greastest to least greatest. I would just go with order or release if you even play part 2 at all.
Although, I know how you feel, it was hard to try and get my friend to play DMC1 after playing DMC3 for a long time. Lol, he still hasn't beat Vergil 3 yet! XD