Perfect Pop Songs

Baby It's You - Smith
Venus - Shocking Blue
Out of Time - Rolling Stones
Mellow Yellow - Donovan
Thunder and Lightning - Chi Coltrane
Dirty Work - Steely Dan
If I Can't Have You - Yvonne Elliman

@bdp24 

Kudos for mentioning Emmitt Rhodes, along with Don Dixon & Marti Jones; so, I'll add:

"Praying Mantis" & I Can See the River" - Don Dixon
"Walk Away" & "Tourist Town" - Marti Jones  

Crimson and Clover - Tommy James & The Shondells
She's Not There - The Zombies
Pretty Lady - Lighthouse
I'm On Fire - Dwight Twilley Band
I Wanted To Tell You - Matthew Sweet
Wake Up Sleeping - The Saw Doctors

Under the "popular" banner, I'll add:

"The Look of Love" - ABC. A brilliant synthesis of new wave, Motown and Bacharach styled orchestral ballad. The Bowie & Ferry styled crooning is the icing on the cake.

"Walk On By" - DIONNE WARWICK. Speaking of Burt Bacharach.....

 

My criteria for this subject is what songs are so good (in all or most of the five areas the OP mentions) that you cannot become tired of it, even if it was massively overplayed. The first few songs that immediately came to mind were:

Tired of Waiting - The Kinks
Nothing But a Heartache - The Flirtations
There She Goes - The La's
All I Want - Toad The Wet Sprocket 

@slaw  How on earth did it take over 60 posts before someone (you) remembered to include California Dreaming? "Just Dropped In" was also an excellent choice!

Check out Edie Brickell & The New Bohemians cover of "Walk On the Wild Side." It's very faithful to the original. If you don't melt when she sings "Holly came from Miami, FLA....," you might want to check for a pulse.

"Fool If You Think It's Over" is a great song; but, Chris Rea's voice sure has changed over the years. However, he's continued to make good music (albeit, less poppy). "On The Beach" is a pretty sweet track.

Under the "Pop" genre, I'll add:

I'll Be the One - Badfinger
You Got Me Anyway - Sutherland Brothers & Quiver
Idiot - Robin Lane & The Chartbusters
Tiger Nights - The Bongos
Torn in Two - Shoes
That is Why - Jellyfish

Just because a song doesn't become popular, many of the songs people have mentioned in this thread should've been popular. In the case of the Beach Boys, listed below are the highest chart positions of some of their best songs:

God Only Knows - # 39
Don't Worry Baby - # 24
In My Room - # 23
Surfer Girl - # 7

If you want to know about the taste of an average American popular music fan, I'll rest my case on those numbers cited above.

I am not surprised that "power pop" has dominated this discussion so far. So, now that Motown and R&B classics are starting to get mentioned, here's a few more:

Schoolboy Crush - Average White Band
Until You Come Back To Me - Aretha Franklin
I"ll Take You There - Staple Singers
Use Me - Bill Withers

Somehow, we've managed to forget two very obvious choices:

Be My Baby - The Ronettes
When My Baby's Beside Me - Big Star

Here's a few more less obvious songs from the "new wave" era:

How She Threw It All Away - The Style Council
Gang of One - Bradford
Dig For Fire - The Pixies
The Sound of Crying - Prefab Sprout
Don't Run Wild - The Del Fuegos