Agreed with spleeny, Its the connection not the phones.
Theres a couple of things you could do.
Break the bad boy open & replace the socket altogether. Its a pretty simple job if you know how to solder.
Ive found in the past that if you "raise" the plug a tad the connection improves. Get a piece of rubber & cut it to shape (with a hole in the middle) so it looks like a washer & put it on the end of the headphone plug. When you plug it in it will not go all the way in & may improve the connection.
The only other thing I can tell you (& this may not work) is to get your hands on a mini-to-mini splitter or something similar (see pic) & use it betweem the source & your headphones. It might fix your problem & will prevent more wear on the socket.
Hope that helps.