a simple solution (Since I have RCT2 Steam Version) was to rename OpenRCT2.exe to RCT2.EXE then steam will launch it like the original exe.
I went one step further, I left OpenRCT2.exe alone and created a hard link using Windows mklink command to point to RCT2.EXE so steam will run RCT2.EXE and it actually runs OpenRCT2.exe