Here are well-known / highly regarded builders active in Kolkata (commonly listed in recent industry rankings and property portals). I’ve included a short note for each and sources you can check for projects, reviews and RERA details.

• Ambuja Neotia — large Kolkata-based developer known for mixed‑use and eco-conscious projects (EcoSpace, Udayan). (rivirtual.in)
• Merlin Group — major local player with many premium residential projects across the city. (rivirtual.in)
• PS Group — established Kolkata developer with many residential and commercial projects. (rivirtual.in)
• South City (South City Projects) — prominent for large township and high‑rise projects in south Kolkata / EM Bypass area. (makaan.com)
• Srijan Realty — notable Kolkata developer with several residential/commercial projects. (makaan.com)
• Shrachi Infrastructure (Shrachi Group) — longtime local developer with residential and commercial developments. (makaan.com)
• Eden Group / Eden Realty — active regional builder with mid‑market residential projects. (houssed.com)
• Rajat / Rajarhat / Rajwada groups (regional builders) — several local groups that frequently appear on Kolkata lists for delivered and ongoing projects. (houssed.com)
• Godrej Properties (city presence) — national listed developer with select Kolkata projects and brand recognition. (rivirtual.in)
• Magnolia Infrastructure / Merlin / Diamond / Purti / Bengal Shelter — other frequently listed local/regional developers with active projects in multiple micro‑markets. (houssed.com)

Notes and next steps:

• “Top” depends on your criteria — reliability/timely delivery, quality, after‑sales service, project scale, or resale performance. The sites cited (developer lists, portals and local real‑estate reporting) use different criteria. (makaan.com)
• If you want, I can: (a) narrow this to the top 5 by delivery record and RERA status; (b) show recent/high-profile projects by each builder; or (c) find contact/RERA pages for any specific developer above. Which would you like?