Having collected and read the entirety of the
Marvel Team-Up title from the '70s, I suppose I feel as qualified as anyone to say that, in terms of hit and miss, its stories generally tipped into the latter category for me while they shoe-horned Spider-Man, the standard bearer of the book, into a meeting/partnership with a different character each month. That said, there were a number of gems that were quite readable, some of which even stood out as page turners--in fact, you and I would probably be able to compile a "top 10" list of stories if we put our minds to it. (A potentially interesting topic for a future post, I dare say.)
In your own listing, I hope you make room for a four-part story from 1979 by Chris Claremont and Sal Buscema which, like other MTU multi-parters, drew in more than one guest-star to heighten the story's development and ramp up interest, which had the added benefit of spicing up the cover masthead with the naming of a new player with each installment. In its opening pages, things start off with an attempted mugging of a lady who seems out of sorts in her life, an attempt foiled by Spider-Man--but when the wall-crawler literally slips up and leaves himself open for certain death, our damsel in distress proves to be far more than the confused and helpless person we first laid eyes on.
Obviously distraught, the woman who by all appearances is the Black Widow gains the sympathy of Spider-Man, who makes allowances for the possibility he could be wrong about her and tries to help her collect herself. In the process, he learns her name and her occupation--but for himself, and the woman who calls herself "Nancy Rushman," the mystery of her identity only deepens with unsubstantiated assertions which call her story into question.
Since Spider-Man has noticed that the Widow's costume is insulated*, he suggests she put it on (with hopes that it might jog her memory). Yet Nancy's calm insistence of her own identity only raises doubts with the reader (which makes sense at this early stage of the story) that, despite appearances, she is the former Russian spy we and Spider-Man recognize.
*Something Spider-Man might consider for his own costume--how does he bear the frigid winds of winter while web-swinging through the city at such high altitudes?
Resigned to pick up the pieces of her life, Nancy prepares to change back into her clothes and part company with Spider-Man. Which is when all hell breaks loose, and a thus far unassuming story explodes into new, violent territory.