One thing that's always bugged me about most Japanese robots is that they're...like humans in a big suit. For instance, look at that picture above - it doesn't even look like a robot at all, and some Japanese robots have mouths, two eyes, etc, or like Gundam, have human-ish proportions. Macross is one of my favorites, because the robots actually look like robots.
I guess American robots are better in the respect that they look like giant walking death machines. Batteletech mechs (for the most part - let's just go with the Mechwarrior games for now), look like they have actuaters and pistons and basically like they're built out of metal.
A good compromise between the two are Heavy Gear mechs. At 14 feet tall, they're not the largest, but they're certainly the most plausible humanisque robots around.