The X-52 Pro has been around a long time now, mine is around 8-9 years old and it is the successor to the X-45 which itself was the successor to the X-36. So basically any game made in the last 20 years with joystick support should work with an X-52 Pro or any other modern HOTAS. With that said, the original IL-2: Sturmovik is the ultimate CFS from back in the day. You can go back further of course but there really isn't anything to be had by doing so. Other bargain bin games include Falcon 4 and Janes anything. For something a bit more current, I recommend Rise of Flight, Battle of Stalingrad and DCS world. RoF and DCS are free in their basic form, they charge for additional flyable aircraft, maps and so on. The extra stuff is available to AI and other players in MP, just not you until you pay for them.
IL2: Cliffs of Dover is not something I'd recommend. The official version of the game is complete trash and even after 2 years of patches, still wasn't ready to be released. Some third party modders have picked it up and allegedly made it halfway decent, but I stopped paying any attention to it about a year ago. I would not recommend it unless you can get it for under $5 and even then it might not be worth the headache.