With the classics already mentioned ITT I'll mention my underdog bargain bin favorites from the days when there were PC game bargain bins that did not contain pure shovelware. I personally am quite fond of the two jowood-published (or developed?) autistic/german business sims of Traffic Giant Gold and Transport Giant Gold, they are not ideal examples of the genre but they satisfy my autistic side (I like trains and things running on tracks damn it!). Both were some of the better bargain bin purchases back in the day. Decent laptop games, at least back when they ran on laptops.
Problem is if you can run them on Win 7 or newer OS without issues. I would "demo" them first to check if they work and if they are your cup of autistic tea. The second one has a steam release, seems it has issues on newer systems and I also had them with my bargain bin copy.
Traffic Giant is a public transport economic sim inspired by the german urban public transport experience, only without simulating timed tickets (zone simulation only, although those are automatically defined and not visible). In particular I like the simulation of the population, where every building has a bunch of people who want to go to schools, shopping, recreation or jobs in specific places, and who bitch and rather make the Gretas of the world cry by picking a car if there are too many connections needed or if they wait too long. Also has a fairly challenging campaign with interesting objectives such as "transport 40% of school pupils" that I think are also varied either by difficulty level or they were optional objectives/achievements needed for medals (was years since I played it). My only gripe is not being able to build tram tracks outside of streets (can't build them on grass basically, although you can build train tracks there) and the fact it is restricted to 4 directions for tracks rather than 8 like in TTD (no up/down and left/right, just the isometric diagonals).
Transport Giant is a later game by the same guys and an attempt at outdoing TTD. While lacking the voxel (or whatever it was) maps with elevations due to having a flat isometric map or indeed lacking the terraforming tools of TTD allowing you to reshape landscape, it is a much more realistic sim, including elements such as inflation and economic cycles and loans that aren't OP, not to mention a fairly realistic cost scale (trains cost millions, bridges and tunnels are fucking expensive). AI is dumb as shit though, seriously, the railways it makes are retarded.
One key difference compared to TTD is that the passenger destination demand system from Traffic Giant is also here. One flaw is that apparently all rail tracks need to be in one network (you can't build two separate rail lines) unlike in TTD, you can get used to it even if it feels arbitrary. The campaign though is IMO worse than Traffic Giant, but the game is way better in sandbox mode and with random map generation (not sure if Traffic Giant even had random maps TBH).
The depots/stops can be upgraded with various "add ins" like say restaurant (has high fixed cost but gives good cash per customer serviced at station) and the resource chains I think are better than in TTD with way more resources IIRC and also seasonal production (ex. wheat farms only harvest in August or whatever). Particular the variety of goods cities might want delivered is very big and similar to TTD some resources are unique to the map type (North America, Europe or Australia). It is good enough as its own thing.
Those guys also made Industry Giant and Industry Giant 2 at some points but I never played them, those seem to be industrial conglomerate management sims.
version of RCT going around nowadays? I was watching 
