CU > KGEC >= IEM ... Join Heritage if you absolutely have to otherwise any decent branches in these top 3 will be a better choice...

In case of placement I would prefer IEM and heritage over CU and KGEC. In West Bengal top engineering colleges ( except IIT and NIT) are

1. Jadavpur university

2. Institute of engineering and management (IEM) 

3. Heritage institute of Technology( HIT)