Hi Karthik,
In general, RA are indeed mostly found on bigger aircraft such as airliners. The altitude callouts are part of the CAWS (Cockpit Aural Warning System) which in turn is part of and linked to the GPWS (Ground Proximity Warning System). Here again you’ll find these on most modern airliners and will miss them on most GA-aircraft or jets.
Do note that the crew needs to set a ‘minimums’ decision height manually in order to have the ‘approaching minimums’ and then ‘minimums’ call-outs such as on the A320neo.
I think, but I’m not entirely sure on the following, that the RA are mandatory for aircraft that are rated with CATII ILS-equipment as they make use of the lower DH-minimums in bad weather. As most GA-planes are not equipped with such heavy ILS-equipment they won’t head into such low visibility weather and don’t require a mandatory RA either. Again though, I’m not entirely sure on this last bit but knowing pilots as I do, one will come around here and correct that if need be. 
Happy flying!