The most I've ever had was around 3,000

Bigger would definitely be better.

What I would like is a park a minimum of 1,000x1,000 tiles and a game engine that can handle all the CS I can put in the park. I would also like to have (all at the same time) hundreds of stalls and coasters in the park, dozens of enclosures containing hundreds of animals, the ability to have 50,000 guests & 10,000 staff in the park, with reflective water, with day and night cycle, with shadows in the day cycle, with the highest LOD/geometry imposter settings set permanently that way and all with my existing system and without the game crashing once for any reason.

I would actually like to have a park much bigger than 1,000x1,000 tiles but it would take me more than a year to complete it. Tweaking, adjusting and updating that park would be a lifetime’s work!

But the waiting lines would be horrendous.

LOL!!!!!!!

Well they would lol :d