An aircraft taxied into the incorrect PHL gate at night because the non illuminated jetway sign was attached to the terminal but was adjacent a nearer jetway leading the Captain to taxi into the gate visually aligned with the jetway sign.

Narrative

Taxied to the wrong gate in PHL. Assigned Gate FG-X2. Taxied to FG-X1. It was a dark and wet ramp. During the in-range gate assignment; I checked the airport chart and saw that the gate was located on the corner. When taxiing in; the brightly lit sign indicating gate FG-X2 indicated to me to proceed directly into the ramp because the jetway was extended at about a 45 degrees from the end of the terminal (which appeared to be the corner gate). The approach line to the gate also was at an angle also indicating to me this was the corner gate. Upon reaching the gate lead-in line in the alley; the markings on the ramp indicated that it was for gate FG-X1 and not FG-X2. Because of the ground equipment located out on the ramp; the narrow alleyway and the fact that ground vehicles were stopped on the roadway behind FG-X2; we elected to contact Operations to request a gate change to FG-X1 and they approved it so we taxied to gate FG-X1. The placement of the lighted information gate signs are located near the terminal and not at the end of the jetway and many are positioned closer to the adjacent gate than the actual gate. The extended jetways protrude out at angles and not necessarily perpendicular to the terminal to accommodate different size aircraft. The regular designated gate numbers on the terminals are not illuminated and are not visible at night or from a distance. There were no parkers to meet the aircraft nor was there any rotating light located at the end of some jetways indicating they were awaiting our arrival. The commercial chart gate chart does not reflect the true nature of the placement of the extended jetways and approaches to the gate. (eg.. FG-X2 on the corner has an approach path that is perpendicular to the terminal while gate FG-X1 which is a center gate has an approach which is more conducive to a corner gate than a middle gate). The fact that the roadway is located close to these gates and ground equipment is located far out on the ramp and gate number painted on the ramp lead-in lines is unreadable until close in makes it nearly impossible to correct or maneuver the aircraft safely at the last minute. Gate numbers should be large and illuminated both at the terminal end of the gate and at the extended end of the jetways if they are extended other than perpendicular to the terminal. The rather large brightly lit flight information signs do not need to be as large as they are because they only need to be visible from the immediate gate area whereas gate number signs need to be read from taxiways day and night. Better detailed approach paths on the Jeppesen gate chart would help as well.