Depends on what you want, i do think you can achieve COD quality if youre referring to graphics and gameplay, if youre referring to the full campaign and so on then that may take a while, but say the multiplayer for example, hm, it would take a good experienced team maybe less than a year to clone CODS mp with gamestudio, keep in mind i said good and experienced, i can say this because ive been working on shooters since i got gamestudio, i know most of the pitfalls, your biggest issue would probably be level design and lighting said levels.
Animation can be an issue but there are several workarounds.
If you actually want to do a campaign, then ofcourse that'd take longer, voice acting, tonnes of animation and scripting for example but there are also other ways of telling stories, i personally hate cutscenes in shooters anyway.
You dont exactly have to move from GS but dont expect GS itself to be good enough, check out these extensions:
- Anet [multiplayer plugin, very stable]
- FMOD [for sound if you use A7, i think A8 has better sound features, not sure]
- SHADEC [shaders, to be honest, this isnt complete yet but its quite good, however i'd hate for you to start using it and having to wait weeks for updates]
again it really depends, alot of what we call AAA game quality can be achieved, i think for example:
heelX's SSAO + dynamic shadows + model based level with shaders = good visuals [disadvantage, youre pretty much limited by just the sun as a light source]
baking lights is also ok but to be honest i think it sucks for an fps and i dont know of baked lighting affecting normalmaps, unless you place invisible lights at each source
it really depends on what you want, setting up the player movement, weapons script, effects is super easy for someone with skills, have a look at my youtube page at some past work with shooters:
http://www.youtube.com/user/darkInferno360?feature=mhee#g/utake
THIS vid for example, i'm very proud of it for what it has, however we paused the development for reasons listed above, the level design was just a Pain, not the creation of levels, but the lighting
