You would compare Rangers to Druids the same way you would compare Paladins to Clerics or Shadowknights to Necromancers.
All are melee focused hybrids of warrior and the parent caster/priest class.
In the case of Rangers I think they are a fun versatile and undervalued class. They can tank group content quite well until at least PoP, but aren't going to be used as a raid tank apart from those 15-20 seconds of glory where you weaponshield to give time to position the mob and get CH rot set before a real tank takes it off you.
In classic and kunark they are pretty shit dps wise, in velious they get their atk buffs which help to make monks shine and their archery dps is respectable but will cost you money as endless quiver is not yet available.
Luclin and PoP will be your moment in the sun when you get AM3 and EQ aa's, archery self buffs and suddenly Trueshot discipline (velious) becomes the iwintheparse button every hour or so.
All through the game however the combo of harmony, roots and snares, makes you a pretty good puller as long as you know how to play, and your DPS while not being top tier again is always adequate.