Big improvement
Rollercoaster Tycoon 2 still has many scenarios with even more challenging objectives, but they also have the scenario creator, which lets you create your own park from scratch, starting with a blank chunk of land that you can manipulate anyway you want to make any kind of park you want. If you like spending lots of time on this game, like I do, then you'll love this feature. But if you're a pick-up-and-play kind of person, this may not be for you, because creating the actual park can take a great deal of time, but the upside is: You can make it so there is no money whatsoever! The graphics and overall gameplay haven't changed drastically in this sequel, but there are some improvements that make it more enjoyable and give you a lot more variety to what you can do. Now, for example, you can use the shift key to move blocks and walls up and down and make entire buildings, which you couldn't do at all in the original. This opens many many new doors in what you can do with your rides and park. There are many other new rollercoasters and rides, but the reality is it's not that different from the original, though it is cleaned up a bit graphically and has new features. Plus, the scenario mode is a little screwed up, because there are no scenarios to unlock, they are just all there and there is no clear reward for completing one.
However, I've spent several hours on this game making my own parks and keeping them up, so if you're like me and loved the original, you'll be addicted to this; I have been for years.