SMT IV is far inferior to previous SMT games in all regards. No two ways around it. Above all, it lacks that special something the other games had. The depth, the story.
Play Digital Devil Saga (1+2, they are technically one game), that is what you need.
The funny thing is that SMT IV is still great compared to other games. But the moment I played Persona 4, DDS, DeSu and Nocturne in a row I knew my standards would never be the same again.
And that I may not get to play such great games in a long time.
Devil Survivor is also a splendid game, something inbetween SMT and Persona vibewise. Great combat system (my favorite tactical RPG by far). The second one is inferior in both gameplay and story, but it's still very good.
Devil Summoner (not talking about soul hackers) is an odd ball. It has a special charm, but don't expect anything great. I love it, but it really isn't that great a game by itself - although the main story metaphor is neat. The second one improved on all areas as far as I could notice .. but region locked for me. Too bad.
And yes, SMT is an example of a good use of silent protagonists. It's all in how you do it.