I have professional experience with all listed (both on vendor and user side), other than hyper-v. Nutanix is probably the closest true solution to VMware, although not 1:1. VMware is an excellent piece of tech run by people who DGAF and just want the $.

I like Proxmox a lot, but it is technically and commercially several years behind. There is no moat, and when stuff slides sideways, you need to understand what's going on (e.g a competent sysadmin). That is changing with the recent Proxmox NA announcement, but still not there.

OpenStack is not the same product at all, and is about an order of magnitude more complicated. Much more powerful, but instead of a good sysadmin, you probably want a team (and maybe some core devs).