yup control's are one of the most important aspects in a platformer of this type. Look at a game like super meat boy, which imo has control's even better then the mario games(which is saying quite a bit.) They spent A LOT of time just experimenting and fine tuning because they completely make or break the game. Anyone that played super meat boy knows exactly what i'm talking about the, the game would just be too frustrating if the control's wheren't so tight.

As an aside i think a good setup for this type of game would be using an xbox360/ps3 controller, the directional pad to control mario, shoulder button L1 to jump and L2 to run/shoot fireballs, the right analog stick to control the portal gun and shoulder buttons R1/R2 to shoot the portal gun