"Not fully tested" isn't something I like to hear in association with roller coasters, but here RollerCoaster Tycoon World is having a crack at Early Access.
Your £30/$50 (wince) buys "the core features and content of the game", including the campaign, sandbox and scenario modes, 10 coasters, 30 flat rides, 4 themes, "a full (albeit not fully balanced) simulation", park ops, various stalls and amenities, and terrain editor.
Publisher Atari describes it as "a full-featured gaming experience", but user reviews suggest otherwise, citing little improvement over the beta build, broken basics like road building, and sub-par looks compared with 2004's RollerCoaster Tycoon 3. I fear that 'Mostly Negative' rating will be hard to shift, particularly in light of delays, a change of developer and the sudden switch to Early Access itself.
Planet Coaster looks the more inviting theme park sim currently, but at Frontier's steep early bird prices, you might be best off queuing a little longer.