While RCT2 offers new rides/stalls, scenery objects, and construction capabilities, it is in many ways still very similar to RollerCoaster Tycoon Loopy Landscapes.

Lists of New Additions:

New Rides and Stalls:

ALL 155 built-in Rides and Stalls
Just the new rides and stalls
Note that some rides have been renamed:
~ A matchup of old RCT tracked rides to their new RCT2 names
~ A matchup of old RCT flat rides and stalls to their new RCT2 names

New Ride Design Tools: (note that Roller Coaster Designer is now called Track Design Manager)

Rides in Track Design Manager
Ride Object Data files
*.bmp snapshots of the index photos/blurbs of all 78 built-in Tracked Rides
   Tracks .zip

New Sounds:

DAT files that are actually WAV files
All About the Sounds

New Tracks:

*.bmp snapshots of the index photos/blurbs of all 169 bundled pre-designed Tracks
   Designs .zip

Parkmaker Guides

Tips/Bugreports culled from the Internet

Observations .zip

Here is a gif/jpg collection of creative fan made scenery buildings that were posted to the Internet shortly after the game was released:
(for inspirational purposes only) Inspirations .zip