+1 to c54.

You may be able to do workouts that are roughly equivalent in total calories consumed (but as c54 sez, it's hard), but the energy sources won't be the same and the physiological benefits will differ. Short intense efforts increase demands on the anaerobic systems, burn quickly available but limited supplies of glucose in muscles and liver, and are good for developing speed and ability to cope with, well, short intense anaerobic or anaerobic+some aerobic efforts. Longer moderate activity has to be aerobic and shifts towards using greater but slower-to-access fat-based energy stores. A well-rounded rider needs both.

There is a lot of info in books & on the web (including this forum) on the benefits of different types of riding. And for most of us normal folk, 2-3 interval sessions per week are about all we can handle and get the necessary recovery time. And unless your goal is 90 minute rides, you need to work in longer rides, if only to figure out your nutrition and hydration needs. I can seriously under eat/drink for an hour to 2-hour ride and get away with it usually, but I pay for it if I try that on a 3-4+ hr ride as you can't catch up.