@storyteller: lol, chill man. No give the kid some slack.
That said, he's mostly right. (Personally I feel they are the easiest to build as they DO have the most reference, the problem is most people don't actually think about it.) Again, personally, the raised sidewalks aren't a big deal, though, if you don't want to raise them (which can be done, just make it a new floor segment with more thickness than the normal, characters won't have any problem with collision) you really should remove the texture that suggests they're there, instead go with something like a solid cobble street or such.
Personally, I feel your greatest pitfall in your level design are the big open spaces left in the background.
see attached This makes it rather obvious that the player isn't in a realistic world, as his mind is telling him that there should be a continuation of the street he's on that he can see, even if he can't get to it. Instead he just sees empty sky. Try adding in some other back drop buildings in there or something. Generally, in a city, players should only see sky if they look up.
One other thing that would really make your maps look better, in particular the street scene, are a consistent quality in assets (entities/objects). Right now, your buildings are just flat boxes with relatively small textures applied to them, with small pieces of (odd looking) concrete barriers that have much higher relative texture sizes (in proportion to the size of the object). Those buildings should only be used as backdrops as I described previously, instead, you should fully map out building and structures the player will be close to, as he'll expect to see all the detail in it.
Those are some starting points. You're off to a good start. Just keep working at it, try to learn something from the advice people give ya, and you'll be creating some great stuff in no time.
The voices in my head said I'm normal... o.0
