It depends what the criteria is to be judged 'the best of all time'.
If you go with longetivity, i'd have to choose Asservissante since they're still here.
Les Filles de M. Jacques was a heck of an agency back in the day. When i started hobbying, it was $130 for the first hour, $100 for the extra hours. It was a hit or miss with that agency. You could wind up seeing bombshells (and i did a few times), or so-so girls (and many of them also happened to be very popular among hobbyists). One thing, though....for whatever reason, it seemed that Jacques hated having girls that had become too popular. Maybe he didn't like the fact people kept calling & asking for them specifically....and this may have made it harder for the other girls to get bookings, who knows.
I remember when i'd call, he'd basically ask me what kind of girl i'm looking for and would tell me who he had working who would fit the bill. At one time, he had two girls with the same name (Josee) working at the same time. He'd refer to one as 'Josee from Longueuil'. I saw one of them and had a great time. She was an average-looking girl who had a bit of mileage on the meter. One night, i had already seen two girls that day and still felt horny later on. At around 11pm, i gave Jacques (or his assistant) a call and he told me he could send Natasha over. He gave me a brief description of her and she seemed ok. An hour later, still no Natasha. So i gave him a call again and he told me she was on her way. About 15 minutes later, i heard a knock on my door and in walked a statuesque, absolutely drop-dead gorgeous blond girl with blue eyes and a great body! She extended her hand and said "Bonsoir, mon nom est Frederique". I was surprised to hear her name and said "I thought i was supposed to see a Natasha?" She then apologized and asked me if i wanted her to leave. "Of course not, come on in my dear!", i said. Was i nuts?? It turned out that she had been working at a resto or bar on Crescent street that night and was supposed to finish at 11pm, but had to stay longer, so that that's why she was late. She also told me that she also danced at nearby Wanda's (i stayed at HDLM during that trip), that her divorced parents were italian and when i was surprised that she didn't have the typical 'italian' look, she educated me in that it's not uncommon to see northern italians with her features. Needless to say, i decided to keep her for 3 hours (at that price, why not?) and had a great time. She suggested we meet 'outside the agency' setting in a couple of days and i agreed. We exchanged emails, but for whatever reason, it never happened.
If longetivity isn't one of the requirements to be named 'best agency of all time', then i'd have to vote for Eleganza. John was a master recruiter and many beautiful young women started their 'careers' at that agency. Sure, he pissed off many of them & they left the agency....heck, i later learned he and my atf from that agency were actually an item at the time, but still......an incredible high number of gems wound up being recruited by him and working for him. He rarely fucked up the bookings and the pictures he posted on his site truly reflected how the girl looked. Or at least, the pictures rarely were better than the girl actually was. Several times, i'd look at the pics and tell myself "hey, she looks pretty good and my type". And when the girl would show up, i'd go "Wow! Holy shit! You look absolutely great and even better than in your pictures!"
Back in the 'Jacques' days, other agencies i'd call were "Agence Fantasmes", "Freedom" and especially "Maxximum", who had a great roster of girls and dealing with Jules (whom i later learned was banging my #1 girl at the time) was always a pleasure. I did try out a $100 agency once and had mixed results...i believe it's still in business today (but likely higher rates). But my #1 agency at the time was a high-end agency called "Montreal Girlfriends". I believe i saw most of the girls at that agency other than Lolita, Chloe & a black girl whose name escapes me. But i did meet Chloe at a later time when she started her own agency and she only agreed to see me because she had been wondering why i had seemingly been 'boycotting' her, as she put it. Our initial meeting turned into a wonderful friendship where we'd later meet for lunch or dinner when i'd be in town. I also saw a few girls from 'Sweet Dreams' and 'Alissa MTL', where i met some of my atfs like Melanie (a.k.a. Melanie Cherie) and Rachel (a.k.a. Rachel Morgan), among others. I did meet the then semi-famous "Coralie" at Sweet Dreams (under the name Victoria). She began her career at LFML and was the talk of the boards at the time...such a classy, beautiful girl for only $130 (plus $100 for extra hours).....ah, the good ol' days!!