I buy whatever strikes my fancy, the engine configuration plays a part in it but I look at the total package in looks, handleing comfort and performance. That's why I brand-hop so much, there's so many cool bikes I want I don't want to get stuck in a rut. I'm on my 5th Harley V-twin now, but in between I've had flat twins, flat fours, vertical twins and inline fours, V fours, I like them all.
It occured to me that I'd been riding fours for a long time, and I was tired of water coooled bikes so I got the Thruxton, when that didn't work out I was looking at FZ1's for performance or Bandits because I really liked the one I had and I think the air/ oil coolled GSXR motor is one of the best in motorcycling.
I settled on the Dyna because I like the stripped down no frills look of the original Superglides, the 45* twin is integral in that, but it's the way the total package is integrated not just the engine.
I wish we could get more variety here but as Suzuki has shown, we get full-on sport bikes or retro looking V-twins. If you look at their overseas line-up in the UK there's a ton of cool looking models we don't even get because they seem to feel we're hung up on cruisers and sportbikes. IMO, the UJM has become a retro-look V twin cruiser, at least Honda gives us the 599 and 919.