I have 4, a V3, V4, V4.5, and a music star only the music star is running right now. Technical I just realized I have 5 cause I have a V5 but I'm not on speaking terms with it.
I have 10 Tamagotchi's, but one's broken . I own a V1, 2xV2, 2xV3 (but one's broken), 2xV4, V4.5, V5 and Tamagotchi Mini. I bought them as they were realeased, my favourite is probably the V1 or V2.