Hi and welcome.
Those games that you mentioned are most likely to be supported by the MAME Emulator and Project.
The MAME Project usually starts emulating games after they are 3 years old and they are not exploited commercially by the companies that hold the copyright. (Source:
About MAME section on MAMEDev.org)
Also, in my humble opinion, there are Emulation Sites (Like ZD, or NGEmu that provide Emulation News and Downloads and other related things but not Commercial ROMs) and there are ROM Sites (That provide commercial ROMs, therefore being illegal since they don't own the copyright or have a distribution agreement\license for them) that sometimes also provide some emulation news and downloads.
You don't get to see new generation console emulators (emulators that emulate Xbox 360) for 2 main reasons:
1- New generation consoles are way harder to emulate since the system itself is more complicate, also the systems that would be needed to correctly emulate them don't exist yet.
2- Emulation is not about giving you a way to play new games for free. Emulation is about preserving games that you cannot play today for various reasons including availability (of the console and the physical game) among others.
For the legal issues on ROMs (also known as ROM Images) please check the
Legal Status part of the ROM Image article at Wikipedia.
Hope I helped.