Ahh man that is a tough decision. I like number one for it's mixed sounded and I like number 2 because it reminds me of animal crossing and number 3 is so simple that it's really nice lol. If I had to pick I would go with # 2. Or if you want to do different types of videos, like review videos could start with intro #2 and unboxing could be #1. You know what I mean? Anyhow, whatever you choose will be fine:)
I have an idea, though I don't know the extent of your technical ability, I'll tell you anyway. It starts with an AR card with a picture of your Mii's head and the Mii Maker jingle, your Mii then pops out, and does a pose with the 3DS opeing theme. Then above it appears the Mr.DSiReview Intro motto, replacing the DSi with 3DS so it's MR.3DSReview, with the AR jingle, then cut to a white screen in black text of the game you are reviewing, with the settings jingle. How's that for an intro?