I'd happily list players I've seen from rival teams that are or were world class. No bias, it's a widely held opinion.
I think you're over-rating Gerrard's drive and diminishing his ability. He's always been a good technical player. He's scored more goals than a lot of forwards do in their careers.
He's won countless individual awards, including 3rd in the Ballon D'Or and UEFA player of the year.
None of us have any idea what he'd have been like - but the likes of Mourinho (who wanted him at Chelsea and Madrid), Fergie, Alonso and Zidane all rate him as one of the very best

. Around 2005-2009 there were very few better attacking mids in the world.