BECMI was my middle school crush. We were too young to get really intimate, but we hung out and had a lot of fun in our childish way. We eventually drifted apart and fell out of touch for a very long time. A year or two ago, we re-connected, and even went out on a date; it was fun, but we both agreed it wasn't going to lead to anything serious. We still keep in contact and hang out once in a while.
1E was BECMI's older sister. I thought she was really hot, but she was never interested; she condescended to go on one date with me in eighth grade, and that was it. I keep in touch with her too, a little less than BECMI. I've grown up enough now to understand that we'd never get along - she's got all kinds of emotional issues - but damn, that girl still has one hell of a body.
2E was my high school sweetheart. It was wild and passionate and thrilling, even though there were a lot of times she drove me absolutely crazy. We kept dating into my college years, but as with so many high school relationships, it started to cool; toward the end I started dating GURPS and fooling around with White Wolf on the side, and I finally dumped her for 3E. It was a bad breakup and I've hardly talked to her since.
I met 3E toward the end of college, and she was exactly what I was looking for after 2E - reliable, consistent, steady. She had her life together and didn't keep calling me drunk at 3 AM to beg for a new house-rule, and that was a big relief. Dating her was never as exciting as 2E, at least after the first thrill wore off, but we had a good few years.
After a while, though, it started to wear on me. 3E wasn't unreliable the way 2E was, but she wanted a lot of attention. She'd never be up for some wild and spontaneous sex; I always had to wine her and dine her first, and when we did get into bed, it took an incredibly long time to get her off. I'll give her credit, she tried to spice things up a bit when she realized it wasn't doing much for me. She got herself a set of Tome of Battle bondage gear, and that brought some excitement back into the bedroom, but in the end it just didn't work out and we went our separate ways.
Right about then, I went out on that date I mentioned with BECMI, and it wasn't too long after that that she introduced me to her cousin 4E. We hit it off and it's been a lot of fun so far. She's not nearly as serious-minded as 3E and she's very low-maintenance. She does like some kinky stuff, and at first I was dubious about it, but I got into it pretty quickly. I've never met any system who could get me so hot about DMing. Although she's a little clumsy sometimes, it's totally worth it and I wouldn't go back.
Make whoopie with 4e. Whereas 2e and 3e made accomodations for "realism", all 4e wants to do is game. Poison an undead creature that has no blood running through its veins? Sure! It's quick and it's dirty and you feel just a twinge of shame after running it.
Nitpick: Poison doesn't work on undead in 4E any more than it did in 3E, 2E, or 1E. All undead monsters have immunity to poison and disease. (It's not inherent in the keyword "undead" the way it was in 3.X, but every undead monster in the Monster Manual has those immunities, and the DMG templates like "lich" and "death knight" add them to the monster you put them on.)