I think it's time everyone stops using the ANH/ESB comparison it's from completely different era.Try picking films from this century, from this era of blockbusters (the franchise/sequel era).
I'm going to list high grossing film sequels which were within 5 years of the original.
The TPM to AoC drop seems to be an anomaly, probably because of the quality of these films. They were both received very poorly.
Shrek (2001) and Shrek 2 (2004), $484m to $920m.
The Avengers (2012) and Age of Ultron (2015), $1.51b to $1.41b.
Spiderman (2002) and Spiderman 2 (2004), $822m to $784m.
Sorcerer's Stone (2001) and Chamber of Secrets (2002), $975m to $879m.
Toy Story (1995) and Toy Story 2 (1999), $374m to $497m.
Fellowship of the Ring (2001) and Two Towers (2002), $869m to $923m.
Ice Age (2002) and Ice Age Meltdown (2006), $383m to $661m
Hobbit Journey (2012) and Hobbit Smaug (2013), $1021m to $958m
Thor (2011) and Thor TDW (2013), $449m to $645m.
Iron Man (2008) and Iron Man 2 (2010), $585m to $624m.
Batman Begins (2005) and TDK (2008), $373m to $1.00b
Transformers (2007) and Revenge of the Fallen (2009), $710m to 836m
Pirates Black Pear (2003) and Dead Man’s Chest (2006), $654m to $1.06b
I’m not even cherry picking here, every damn franchise is proving my point.
Why are we comparing The Force Awakens to A New Hope? I know TFA was a rehash of it but give me a break, different eras people.