We are planning on staying at the Alessandro Downtown. I’ve heard good things about it and our next door neighbour stayed there on her trip. She said it was great.
She also stayed at Archi Rossi and recommended it for us.
Don’t know about the others.

You seem to be on a good path. Those are all quality hostels from my reading. I have stayed at Archi Rossi and it was great. I stayed at Jaegers (between Wombats and Euro Youth in Munich), and it was good, but you can’t go wrong with either of your choices there. Rome and Amsterdam look good too…

In Venice: Hotel Venice Villa Dori was the most booked Venice hostel on eurotrip last year by a reasonably large margin.

In Paris: These two always do well. St Christopher’s Inn and Village Hostel

Thanks for the recommendations… For Venice, do you know of any place inside Venice?? I might end up staying at your recommended hostel, but I was hoping to staying on the island.. I do have to admit that staying on the island would be much more expensive…

Stayed in Rome at Alessandro: yes
Stayed in Munich at EYH: yes
Stayed in Cologne at Station Hostel: from what I vaguely remember, yes
Stayed in London at St. Chris’ Village: yes
No experience with the others

Happy travels

In Paris,
I stayed at Le Village Hostel in September 2009. It is ok. I met a lot of great people there.
Located close to Anvers metro stop and Sacré-Cœur Basilica.
Grocery, laundry, shopping, restaurants all close by.
They have an ok breakfast. They do have a lock out during the day, so that they can clean the rooms. I can’t remember the hours.
No bar (but they do sell beer and grocery is really close and has beer & wine), no lockers, (but they do have a luggage room) , try to get a bottom bunk there are no ladders to get into the top bunk so you have to hoist yourself up.
I would stay there again.

In London,
I stayed at Palmers Lodge in September 2009.
Close to Swiss Cottage tube stop. It’s about a 15 minute ride into the city.
Nice breakfast, Good bar at hostel and cheap meals in the evening, free internet just sign up for a time. Lockers under the bunks. Very social hostel met a bunch of cool people. I would stay again.