Benchpressing is a multijoint movement, individual biomechanics and muscle make-up can cause other parts than the chest getting the brunt of the stress, but do not debunk the bench yet!
Studies have shown that people just starting out in the first months were able to build more chestmass with pecdeck machines than benchpressing because benchpressing requires much more neurologic coordination to get the right groove at an adequite weight, however after a while, when coordination is established and the weight has surpassed a certain treshhold free weights become often superior to the machines.
One of the best exercises for chest in my opinion is the incline and flat dumbell press. It"s A marriage of relatively heavy weight and decent isolation. Bang out 6-8 reps of these.
A nice program would be:
8-6-6 incline (35-40 degrees) dumbell press
8-6-6 low-incline (15-20 degrees) dumbell press
8-6-6 low-decline (-15 degrees) dumbell press
You may have heard warnings about training a muscle not to often and taking enought restdays etc..... Well guess what , the guys with the biggest chests i know, train their chest EVERY DAY! ((maybe they have a genetic advantage for chest and thats why they love to train it so often, but still....) Key thing is that they do this every day attack only for one musclegroup, otherwise I would be sure they would burn up in 2 weeks.... Also they do very LOW VOLUME (total 4 sets) everyday so that the muscle recovers faster . You still have a special chest day where you do more sets (like the routine above) but also here the volume is limited to 9 sets total (as opposed to the usual 12-16 sets).
Let's say you train 5 days a week and have the weekend off, you might attack chest as follows:
session 1
8-6-6 incline (35-40 degrees) dumbell press
8-6-6 low-incline (15-20 degrees) dumbell press
8-6-6 low-decline (-15 degrees) dumbell press
session 2
8-6-6-8 incline benchpress
session 3
8-6-6-8 flat benchpress
session 4
8-6-6-8 decline benchpress
session 5
8-6-6 incline (35-40 degrees) dumbell press
8-6-6 low-incline (15-20 degrees) dumbell press
8-6-6 low-decline (-15 degrees) dumbell press