Is a man’s penis supposed to stick straight out when erect?
A man’s penis can point is many directions, almost all are normal. The angle an erection will have depends on the amount of skin available to be stretched. Circumcised men will have penis’s that are closer to perpendicular to their body (they’ll stick straight up). Uncircumcised men are more likely to have erections that are right angles to the body (they stick straight out).
Of course there are going to be exceptions to these generalities. Some doctors will cut more skin away than others while performing a circumcision, which will have an impact on which direction your erection will point. There are no physical advantages or disadvantages in relation to which direction an erection points.