If you're just starting out or coming back into the fold, R-Type Final is actually not a bad place to start. The slower pace, and less complex level design might bore some players, but with over 100 different ships to select from, many affecting the environment differently, as well as different paths and ways of advancing through each stage, it's a little bit more meaty than some are letting on.
The biggest downsides of the game to me are that you do have to invest a lot of time to unlock the ships and such and if you're not into that kind of grind it will put you off. Also, there is some bug-related/technical/unintentional slow down that shouldn't really affect an old school shmuper much, but it's there.
The R-Type series has always been a methodical, "thinkers'" shooter that relies more on enemy AI and level design than huge bullet patterns or frenetic speeds. As the official last game of the series, the game mostly lives up to it's predecessors--giving fans of the series what they expect without pushing the envelope too much.