#2 The PG Era (2008-2014): Chris Jericho
Even though Chris Jericho wasn't always with WWE during these years, when he was, Y2J could build a feud like no other, as a devious and conniving heel. Just as the PG Era began, Jericho was in the middle of an amazing feud with the legendary Shawn Michaels. This feud was a great example of how "The Ayatollah of Rock n Rolla" could push the buttons of the WWE Universe in such an incredible way whilst also making his babyface counterpart seem so justifiably heroic.
Jericho's feud with wrestling legends, Ricky Steamboat, Jimmy Snuka and Roddy Piper up until WrestleMania 25, tag team title run with Big Show as JeriShow (2009) and World Title rivalry with Edge were made so great by him upping his heel persona even more.
He did this by introducing new witty insults such as 'hypocrite' and 'parasite' into his promos, on opponents and crowds alike. It was a pity when he departed from the company in late 2010.
The good news though was that Y2J then came back to the WWE in 2012, as heel-ish as ever, and really put the babyface CM Punk over as a strong WWE Champion in their bitter back and forths. Jericho never lost a step.
The fact is, everything Jericho did as a heel in the PG Era was memorable, and I can't say that truthfully about anyone else. If only heels nowadays were like Jericho and cared more about getting their opponents cheered than themselves cheered. That is what a true heel should do.