I'm in this boat.
I still have my '91 is, but I have an '04 325xi for daily duty now. I'd keep the e30 as a summer car, but I have 2 wheels for that. Track car? Perhaps. There is occasional AutoX about 2 hours from me. Rationally, I should sell her, but I know if I drive it at all, or get the wrenches out and tweak ANYTHING, I'll fall in love all over again. The e46 is a beautiful, quiet, smooth, surprisingly economical car that I simply cannot fall in love with on the same level. No joke, I shed a big ol' weepy man-tear the last day I drove my e30 home from work.
It's been an incredibly journey together, and it's so hard to part.