The real-time (or pausable real-time) combat system in this game was incredibly fun and addictive, combining the fast-paced fun of a beat 'em up brawler (or fighting game) with the deep mechanics of a role-playing game, almost like Final Fantasy's Active Time Battle system adapted into a fully real-time hack & slash combat system. On top of that, it allowed up to three players to play together cooperatively, with the second and third players able to drop in and out of the game at any time, again like a beat 'em up.
While there have been plenty of great battle systems since, no RPG since has had me keep coming back to experience a game's battle system over and over again the way Secret of Mana has. This game, for me, is the 'magnum opus' of action RPG battle systems.
Another game that inspired me was Clannad. Its themes revolving around family, as well as life in general, resonated with me in a way no other game has done since.
And finally, Final Fantasy VII also inspired me. Not only did it get me more into RPG's, but the game's real highlight for me was that mind-blowing Zack twist, which I found to be an eye-opener (and one that even most FF VII fans often overlook in favour of the Aerith twist).
The nameless protagonist of Dragon Quest V is one of the best examples I've seen of a silent protagonist. Without saying a single word, I felt like I could sympathize with him far better than most of the talking protagonists out there. And the reason is because we observe him growing up from childhood into adulthood, in times of happiness and sadness, giving us an idea of how he might be feeling in certain situations without ever hearing a single line of dialogue from him.