Hehe. Well each one of us surely has his own preferences. No win situation here.
Yes, everyone is different. For me.
PES5 > ISS Evolution 2 > ISS Evolution > PES 2011 > PES3 > ISS 98 > PES2 > PES 6 > PES 2010 > PES4 > PES (didn't play that game much, stuck with ISS evo 2 instead)
Now the shit...
PES 2009 > PES 2008.
Thing is PES 2011 is the best quality in gameplay of the series by quite a margin. It's the most realistic football game you can get at the moment. But it's impact at the time is why it's 4th on my list.
Also i liked PES 2010, but let's not dismiss the fact it was heavily broken!