i think each support has their pros and cons. i will list few of my fav hard support

Lich
Pros - good laner with saving ability. Min control spell, high dmg team fight ulti
Cons - no pushing power, channeling disable spell. Cant really clear creep to def high ground

Lion
Pros - One of the best control support, high dmg burst ulti.
Cons - no pushing power, cant really clear creep to def high ground. not really a good lanner and no protect skill until you have forcestaff or glimmer

Shadow Shaman
Pros - Pushing power, creep clearing, good disable
Cons - Damn slow, not a good lanner, no saving skills until you get forcestaff or glimmer. Needs lens to increase cast range too, normally support 5 have 1 or 2 items per game max... so have to pick around glimmer/forcestaff/sceptar/lens

Rubick (one of my fav)
Pros - good lanner, increase other spell using cores ability, easy to clear creep wave for de-push
Cons - very dependent on enemy heroes. no pushing power, no saving spell until you have forece staff or glimmer

Lina
Pros - extremely good lanner, clear creep wave to def high ground, push out the creep wave easily and transform into late game dmg dealer when needed
Cons - unreliable stun, no saving until forcestaff, glimmer

CM
Pros - good lanner, provide passive mana regen for spell users to win their lanes, easy to clear creep wave to def high ground, good team fight spells
Cons - slow paper like hero, needs bkb to use ulti, disable skill cannot cancel certain channeling spell (PUDGE ULTI!!!!! you know how many pudge you will see). no saving skills until forcestaff or glimmer

ogre
Pros - super tanky in early game, blood lust enable your right clicking, jackpot way of burst dmg, can turn into cores late game if needed (no joke, i get abyssal blade to delete snipers/bone/drow/invoker for so many games as a support 5)
Cons - no pushing power, no wave clearing to def high ground

i think thats all the heroes i like, of course there are heroes like vs, aa, kotl... but i found it harder to use and require more teamwork in public game....

i like supports that can stall the game defending high ground and stun because most of the time your cores do not have stuns or creep clearing and best can turn into another core like lina.

my current fav support WR(didnt mention), lina and lich. i played these 3 supports only until they change again, they nerf my CM so many times... with the lastest GPM talent gone, i felt CM is no longer a hero as she needs glimmer and bkb.