I want to plan my five day trip to Rome, but don't know how long specific sights will take to see. The first afternoon I will be arriving, with my boyfriend, from Denmark via train and meeting my parents at the airport after they fly in from Seattle. We are planning to just walk around and get oriented. The next three days are entirely in Rome, and we will be leaving in the evening (5ish) of the fifth day for Tuscany. I am planning on seeing the Vatican sights on the day of my departure.
Please, anyone who has gone to these sights, tell me how long (even a rough estimation) they take to see and what sights you would group with them. My boyfriend and I are architecture majors and want to really look at the major buildings in each area, but aren't as concerned with seeing the art (we want to see some, but not all). I have tentatively grouped them by area, but don't know which areas to combine into one day.
I want to see:

Ancient City
The Roman Forum
Palantine Hill
Fori Imperiali
The Colosseum
Capitoline Hill

Centro Storico
Piazza Venezia and Via Del Corso (
Pantheon
Piazza Navona
Chiesa di Santa Maria sopra Minerva

Piazza di Spagna and Environs
Spanish Steps
Piazza del Popolo
Santa Priscilla catacombs

The Vatican City
Basilica di San Pietro
Sistine Chapel
Castel Sant' Angelo
Vatican Museums-----4-5 hrs min.?

Trastevere
Tempietto

Termini
Church of Sant'Andrea al Quirnale
Quirnale alle Quattro Fontane

This is really impossible to answer - it just depends on your level of interest. I have seen people in and out of the forum in an hour. But if you're really interested and want to see details you can easily spend a whole day. Most of the sights are the same.

If you consult a Michelin guide I think they still put an estimated time for sight - for a reasonable - not just top line - view of things.

This is really hard to answer. I also found that even if it's technically possible to see X number of sights per day, you might be overwhelmed by the time you get to (X - 2) or so.

I suggest taking a look at the Blue Guide to Rome and the Eyewitness DK guide to Rome to get some ideas.

I have to concur with the other members who posted replies. I was just in Rome last November and unless you have guided tours for the St. Peter's Basilica, Sistene Chapel, etc. you can each up a chunk of time just standing in lines.

Buy Rick Steves' guidebook for Rome. It'll help you organize your time.

If I were planning to see the sights you list, my schedule may look like this:
Arrival Day: Check in to my hotel in centro storico. See the Pantheon and Santa Maria Sopra Minerva which is next to it. Then walk over to the Piazza Navona. Have a drink at one of the cafes there or get a gelato at Da Quinto and sit on a bench in the Piazza. Depending on the time, return to hotel for a rest or walk to Via Del Corso to join the pre-dinner passagiatta (evening stroll). Walk up to Piazza del Popolo where you can visit the "twin churches" and Santa Maria del Popolo which has a chapel designed by Raphael. Have dinner in the neighborhood (Buca di Ripetta is good) and afterward walk by the Spanish Steps at night.
Day 2. Walk to Via del Corso and go south this time toward the Piazza Venezia. Continue on to Forum and other Ancient sights. Depending on the depth you wish to explore these, this can take most of the day, especially if you add a visit to the Capitoline Museums. Walk back to centro storico through the Ghetto and pass the ruins in the Largo Argentina. You don't say when you are going to Rome, but if it's in the summer and you have more daylight, you could visit the Tempietto and have dinner in Trastevere.
Day 3. Vatican. The Sistine can only be seen by going into the Museum. Even if you don't want to spend a lot of time with art, it's hard to spend less than two hours in the Museum/Sistine due to the long corridors and crowded rooms. If you can, follow a tour group out of the Sistine and you can avoid the long walk back to the Museum entrance and the even longer walk back to the Basilica. After visiting the Basilica, walk along the Borgo Pio for the medieval architecture and find a place to eat lunch before visiting Castel Sant' Angelo.
Day 4. Walk to Trevi Fountain then through the narrow streets to the Piazza del Quirinale. You might catch the changing of the guard at the Presidential Palace. See San Andrea and San Carlo Quattro Fontane. Continue up Via XX Settembre to the church of Santa Maria delle Vittoria for Bernini's famous St. Teresa in Ecstasy. Walk down to Piazza Barberini and up the Via Veneto, stopping in the church of Santa Maria Concezione for a fright. Continue up Via Veneto to the end and take the passageway to the Spanish Steps. You can do all this in a morning if you get an early start, or stretch it out for the entire day, having lunch around the Spanish Steps and shopping.