I've played 2 and it seems for all intents and purposes to be exactly the same, with extra stuff.
BUT, theres 3 very small minute details that shouldn't matter at all, but which seem to nag away at me until i go back and play the original.
1) All parks are unlocked from the start. This should be a good thing, but i like to feel like i'm being rewarded for playing each level, and theres a sense of progression when you unlock a new level.
2) Parks are either charge for entry, or charge for each ride. In the original i liked to make entry free to start and run most rides at break even untill my big crowd drawing coasters were installed, then i could jack up entry prices and slowly reduce ride prices on everything except for my brand new ++ shiny coaster ++
3) No speed boosters on roller coasters. WTF? i mean seriously how am i supposed to kill people? The best i couild achieve was about 97kph on a coaster with a stupidly large launch hill, and it took AAAAAAges to build. Sure it was fun, but it would be a bitch to make a nice line of syncronized death jumpers™ like i can remember doing long ago.
1) I get where you're coming from, and I think I agree.
2) I honestly don't mind the charge for entry/charge for rides and I like the idea of "money is no object" scenarios. Although, I never manipulated the prices like you seem to, though. I did prefer charging ride prices over park entry, however. Actually, I would manipulate the prices in the exact opposite way. Charge like $30-50 entry fee and make the rides free until I have like 3-4 coasters with High excitement, then remove the entry fee and charge $4 per ride on the coasters.
3) That could've possibly been why they removed them.
People were only using the boosters to create death coasters. I remember that there wasn't really a necessity for the boosters outside of maybe the powered launch coasters. Now that I think back to it... You COULD technically keep a coaster going at a constant 30-35 mph by abusing boosters and brakes, but I wouldn't really bother with it.
My one main complaint with RCT2 is that it's just way too complicated right from the start. Like you mentioned, you can choose any scenario you want right from the start... so which one do you choose? At the beginning of each scenario, you have like 10 roller coaster designs to choose from, and it's difficult because you have to know how to build each one so that it gets a good rating. The scenery functions are much much better, too, but again, extremely complex.
It's like RCT2 was designed for the people who avidly played and completed RCT1. I haven't yet completed RCT1, but so far, I prefer it. To be fair, I don't usually play management sims, though.