What are the alternatives to the Proxmox virtualization system?

Question

Virtualization

1. Tell me what are the alternatives to proxmox?
2. What are the pros and cons of certain solutions?
3. Proprietary or free?

Answer 1

1. Yes, there are a lot of them.
2. worth the money.
3. see the previous paragraphs.
Cons: Costs money.
plus: for the money you get a support, not on the forum, but close to realtime.

Answer 2

Let's start with the fact that Proxmox is not a virtualization system :) The system there is KVM, and Proxmox is a management environment.
There are usually two alternatives - Vmware ESXi and Microsoft Hyper-V. There are tons of materials on Google about the pros, cons, comparisons and everything-everything-everything - comparing ESXi and Hyper-V can cause a fierce holivar, comparable to Linux vs Windows (and actually partially it is :D )
Both enterprise-grade
Both cost money (in normal configuration)
Both have advantages and disadvantages