virtualbox.org

SUSE Studio has a wizard to allow one to create one's own SUSE distro.

Is there an app/website/wizard where I would select the VM parameters (disk size, RAM usage, shared folders, etc) plus the apps which I would like to have installed, and generates a virtual machine for me?

Yes indeed. That program is called "VirtualBox". It's mentioned quite a lot around here, so have a read of the user manual.

Though not "plus the apps I want installed". VirtualBox is a PC hardware simulator, it knows nothing about apps.

Well, you could build a VM, install whatever you want and then export it to an OVA for example. Same end result as your SUSE Studio, just a little bit more... hand massaged/involved.