It's my understanding that the cruise ship port is nowhere near Cairo.

Cruise ships dock at Alexandria. From there you arrange with cruise line for the day trip to Cairo and visit to Giza where you'll find the Pyramids and Sphinx.

The ships dock in Alexandria or Port Said, far around 2.3 hours
so you have enough time to visit Pyramids and Sakkara or Egyptian Museum

I'm sure Travelline did NOT mean the ship is only in port for 2 to 3 hours. Maybe s/he meant 23 hours?
In any case, YES some ships do come to Egypt. Like Travelline did make clear - they will dock in either Alexandria or Port Said. Sometimes both. IF at all possible, pick a ship that comes to Alexandria rather than Port Said. Port Said is a MUCH more difficult port to work with for tour companies. And your time to see the sites you want to visit will be a bit less because for the drive to Cairo they make everyone wait and go in convoy. That means from the start you are traveling at the speed of the slowest passenger on the whole ship. Going back to the ship is not as regulated, but obviously you have a time you MUST be back to the ship by.
From either port it will take 3 hours to drive to Cairo...and obviously, 3 hours back to the ship.... so start out by subtracting 6 hours minimum from the time you have in port. Depending on which day of the week and which port you are talking about, the amount of time to see the museum and the pyramids will vary. IF you are super nervous, take the ship tour. It will cost a fortune, you will be with 500 of your new best friends probably, but you will see the pyramids and museum....Mission accomplished.
If you are more adventurous and want to see/do a bit more, try to find a ship that spends the night, such as the NCL Jade. You can come to Cairo the first day, spend the night, and go back on Day 2 - so much to see and do if you have the time. It can be a great little stop.

"Your new best friends probably, but you will see the pyramids and museum....Mission accomplished." CC, that is EXACTLY what i am looking for! I was thinking about going with the Celebrity Silhouette, as they have a holy land cruise that goes 3 times in the fall i think. I went with celebrity in March for central and south America and can’t say enough good things about that cruise company!!!!

DARK MAGIC - Have a great time doing it anyway you like. Everyone should choose their best route.

My first time in Egypt was on a stop on a cruise and it was the most exciting day trip of the cruise. Like you, I only wanted to see the Pyramids and the Sphinx. But once I got there a funny thing happened. It was such a thrill to see those sites, it only made me want to see the rest of Egypt. A few years later I was fortunate enough to return and it was fantastic.

But to each his/her own, I'm sure it will be a lovely cruise and an exciting day in Egypt.