Zoocoustic said:
-Both took forever for the band to release (4 years each from previous album)
True, but both times U2 released other material between the studio albums. Notably, "Hold Me...Kill Me" and "Original Soundtracks 1" and the 1990-2000 "Best Of" with two new songs and several updates.
-Both had a popular lead single which did not represent the album
This is debatable. "Vertigo" is far more popular than "Discotheque". People began to loathe that song. Unfair perhaps, but I think this speaks about its popularity. "Discotheque" may have cracked the Top 10, but it fell from the charts fast. "Vertigo" lingered - not as long as "Beautiful Day", but it was a far more popular track. Also, I'd argue that "Vertigo" represents HTDAAB far more than "Discothque" did "Pop". As this could be a long argument, I won't discuss that here.
-Both were called mediocre by many critics (rare for a U2 album)
Actually, I think you are wrong here on both counts. "Pop" was heavily praised upon its release. HTDAAB received very strong praise, even from sources not known to praise U2. Some critics changed their tune once "Pop" started to fall down the charts, but this just shows how useless music critics are.
-Both debuted at #1 on the charts
This is true.
-Both fell fast from the #1 position
In the SoundScan era, precious few albums hold the #1 spot for long. It's particularly challenging to do so during the busy holiday season when big albums are released weekly. What's important to note is that HTDAAB spent the holidays in the Top 5. "Pop" spent a scant 3 weeks in the Top 10.
Of course, chart position can be meaningless. ATYCLB also spent a scant 3 weeks in the Top 10, but it sold nearly 3x as many albums as "Pop". And that's where the true value is - sales. To date, HTDAAB has sold over 1M more albums in the U.S. than "Pop". Give HTDAAB another hit song or two and a successful tour and it should be able to come close to ATYCLB's sales.
So while there are similarities, there are more differences.