Kind of some loaded questions, but I’ll do my best to answer.
For the first image, I dont imagine anybody would retopologize a model like that for a game. Not in the sense of wrapping all those parts with low res geometry anyways. How much of the shape you would try to capture would certainly come down to the scale. If that guy were as big as a building then you would try to deliver a lot of the shape, but typically those kinds of details would be in the texture. You would go in and try to capture the silhouette and all the big shapes, but the materials would carry the load… and you couldnt really project the details off something like that either. That model would serve more as a concept.
For the 2nd image, those parts (minus the plane of course) are within game res. Again it comes down to the scale of the object in game, but those meshes dont look too dense. You would definitely remove all those creasing loops near the bevels and borders since they ramp up the poly count without contributing much to the overall shape.
Sorry its a tough question to answer. Your poly budget can be dependent on many things. What platform is the game targeting? What kind of game is it? Is the piece you’re modeling the main focus “hero model”, or is it just a random prop? Is the game going for realism, or is it stylized? How close will the player get to these objects? Lots of factors to consider.
A lot of times your art director will make the calls on poly budget. Sometimes you’ll go back and forth before the model is finalized. A lot of it just comes with experience though.
I guess you already have Cry Engine, but you should also download UDK and Unity as well. Check out their built in assets and you’ll get a good idea of whats acceptable in game. Also, if you look around online you can usually find a lot of game models in obj format, sometimes from big titles.
Hope that helps.
