Gerrard was versatile, but not adaptable — a paradox very similar to the one presented by Arrigo Sacchi (In situations like that, I just have to say, Gerrard's a great footballer, but perhaps not a great player). In every role he required the team to be built around him — hence why he was shoved around to the right wing or to the AM spot at his very best. Him performing as a DM later on was also a very questionable idea — he provided lot of creativity, but Liverpool really suffered through the middle. It's unfair to judge his whole season by that performance, but the infamous slip highlighted the biggest issue that he had when playing in that role.
Lampard, on the other hand, only ever played as a CM or as an AM, I think, but he was always someone who complimented the team rather than someone who required the system to be built around him.