your starting simple, which is great! on the second one, if you keep all your letters the same sort of height it'll look better... like if you compare the size of the Z to the U, its quite a big difference, na mean? that's not to say that all the letters have to be the exact same in height, but when it's a straight simple and you change the height alot then it jus don't look all that good..
the Z and the E are the strongest letters in the 2nd piece, the U and N don't fit in that much...
also, you should learn about 3d, as yours isn't right... the vanishing point, perspective, etc... it's all in a thread here:
perspective drawing and 3D
also, if you haven't checked this sticky already, i suggest you do...
NEWB's LOOK HERE