Whenever we come to Frankfurt which is around 3 to 4 times per year we stay at the Marriott. Staying at the Marriott is knowing what you get. And this is always good.
American style interior, super comfortable beds, very clean and nice staff.
We always stay on the executive floors from where you have a very nice view either over the city or the landscape south.
It is located right at the fair ground which is close to the city centre. Public transport is right outside the entrance.
Very recommendable is the breakfast. They offer a highly various, fresh and delicious buffet. Even if you do not stay at the hotel it is a place to have breakfast.
We will always come back.

the hotel has a good position in the town(near a conference center and metro station), but in the room was too cold and also in restaurants and in the conferences rooms. the bathroom is too small and the door produced a lot of noises when moving.the staff was nice. the breakfast was quite good, but can be improved (the coffee was tasteless). the food on bracerie ici was horible(do not eat coq au vent) and I wait 2 hours for it, but on champions bar was quite good.

Conveniently located right opposite Frankfurt Messe, we originally thought this was too far out of the City Centre but we were wrong. It is easily walkable form the Central Station but also has a Tram stop right outside, 3 stops to the station. Usual Marriott comfort, especially bedlinen and pillows but unusually also offered in-room tea and coffee making facilities also with take away cups

The Marriott at Frankfurt Messe is a solid business hotel. Its price is reasonable, rooms are clean, large bathroom, it is centrally located, close to public transportation. Also there is a little shop in the hotel to buy things like water, toothpaste and stuff. The Bistro sells tasty sandwiches and the staff is nice.
On the downside, it is a huge rather impersonal hotel and there are no shops and few restaurants near. Its ok to stay for business but I suggest a smaller, more cosy place for vacation.
For business stays I had two beefs:
1. The internet access is rather pricey (~6€/hr or ~20€/day). Hotel Maritim (which is very similar to the Marriott, across the street) offers Deutsche Telekom WLAN, which is about 35€ a month and is also availabe at other hotels, in trains and other public places.
2. When you stay longer (weeks or even months) you always get the situation that no rooms or only very expensive ones are available, if there are Messe Events. That is of course a problem with all hotels close to Frankfurt Messe.