Mountain biking is definitely more exciting but if you’ve never hit 50+ mph on a twisting mountain descent on tires 1" wide then you’re missing out! That can be every bit as fun as a fast techie trail. The pizza analogy is a good one – it’s all gooooood.
I love the fact that I have a great mountain bike and a great road bike. I have incredible singletrack – and several options – right out my front door as well as amazing mountain roads (without much traffic to suck the exhaust from). I have friends that love to ride both. One of the hardest week-end decisions is what and where to ride – what a great dilemma!