Two Point Hospital is very much the spiritual successor to Theme Hospital and I would have no problems pointing people towards it first rather than Theme Hospital.
I have extremely fond memories of playing Theme Hospital back on my PS1 but it does have some rough edges.
+1 very very much the spiritual successor, and I think even some of the same developers.
The negative side of course is that they have not really added that much in terms of new gameplay mechanics in Two Point Hospital compared to the original, and a bunch of the levels are DLC so are extra money. But hey it is fun.
Give it a try, this is one of the few ones that I have played and enjoyed.