Super Vegitto- The proportions seem correct, I like how you skinned the body. The face it good, but the skin seems stretched horizontally, making his eyes seem to wide. Also, about the mouth...when someone opens there mouth the top lip isn't suppose to extrude so high, the deformation lies in the bottom jaw.
Gohan [cell saga] - Body proportions look correct, the head is to large though in contrast with the body. Shrink that a bit and it should come out nicely.
Gohan normal, ssj, ssj2 - The torso and above are built well, but the pants need more shape around the pelvis, I notice you extend the crotch to low, raise it up a bit because right now he looks like he has no thighs.
Frieza 2nd form - Good model, good skin, but to fix the leg proportions just select from the pelvis down and then lightly scale it horizontally then scale it vertically about 2 inches (measure on the screen
)
Trunks & Goten - The skins seem smudgy, I liked your old ones better. Also, the shape of the pelvis, raise the crotch, make them have thighs. Also the fold placement on the skin doesn't match the modeled shape, maybe change them to fit the shape better.
Overall you did a good job, the models look good only with a few errors. I'll be waiting to see that Form 1 Cell