It certainly wasn't the first one out there. I knew that Monopoly's Free Parking game came out back in 1988. And Settlers of Catan and Starfarers of Catan had their two-player card versions out as well.
Still, San Juan was ahead of the pack of turning board games into card or dice games.
And San Juan definitely has its own identity outside of its parent Puerto Rico. It shares a theme and the mechanic of role selection with Puerto Rico but it also helped create the genre tableu builders as well as multi-use cards. San Juan has its own legacy.
I first played it very early in my gaming experiences. I'm not sure I had even started collecting games at the time. It was after I had been introduced to Puerto Rico and was playing it with a small circle of friends at least once a week.
Since we already knew Puerto Rico so well, we were able to pick it up almost immediately. At the same time, cards being buildings, money and goods was amazing. (Truth to tell, still is)
In fact, I ended buying San Juan years before I bought Puerto Rico, because it was portable and played down to two and everyone else had a copy of Puerto Rico.
San Juan led the way for other tableu building games with multi-use cards, Race for the Galaxy and Glory to Rome being two of the highlights. I've played a lot of both of those games and I would not only describe them as deeper and more complex but actually better than San Juan.
Not because San Juan is simpler and lighter. Neither of those two traits makes a game worse, although I have friends who would tell me I'm wrong. No, it's because I've found San Juan has really one fundamental, overriding strategy. Getting big buildings out. And luck
of the draw plays a big part in who gets a chance to play them. (Both Race for the Galaxy and Glory to Rome avoid this by having multiple ways to get points)
Despite what I do think is legitimate flaw, I have gotten a lot of play out of San Juan and I have had a lot of fun with it. It is still in my collection and it is a game that still calls out to us to get played.
Frankly, that's because it is lighter and shorter. Between the different roles and the different powers of the buildings, it offers a lot of choices and different experiences in that short playing time. In addition to being a great game to help teach other games like Race for the Galaxy, San Juan gives me the experience of playing a big game in a short amount of time.
San Juan isn't a perfect game. However, the richness and fun of its play vastly exceeds the flaws. I have had over a decade of fun with it. It was one of the first games that opened my eyes to the possibility of how a boardgame could be adapted to a card game. At the same time, San Juan is not Puerto Rico the card game. It is its own fascinating beast.