Rollercoaster Tycoon
This. This game was my childhood. I can remember making an awesome park on Evergreen Gardens, 32 roller coasters, 10G a month and before my old, old computer got replaced, it was in the 68th year with 780,000 dollars. I also built it to compete with a friend of mine. We always tried to one up each other, he would build one ride on his park, I would build one. It became a roller coaster arms race.
That game and Sonic the Hedgehog 3&Knuckles