I've been to Singapore, Malaysia (KL, Langkawi) and India (Mumbai, Agra, Gujarat, Mussoorie, Dehradun, Allahabad, Pune).
Singapore has got to be my all-time favourite - the people are friendly, the food is beyond amazing and it's such a little town/country, that I fell in love with everything about with what makes Singapore what it is!
I have visited Singapore, Thailand and Malaysia. lots of eating and lots of shopping is what I did in all three countries. I loved experiencing different cultures...have to mention the hotels - friendly staff and clean rooms everywhere we stayed!
I have travelled round Malaysia, Cambodia, Singapore, Thailand and have visited Indonesia. I loved visiting the amazing temples within Cambodia and the people there were just gorgeous. It's so hard to pick a favourite place, as they are each so different with their own personalities. I've been to Singapore a few times, and always had a wonderful experience. We have friends there, so it's a good holiday to catch up with people. I enjoy Malaysia and Thailand and the fact that the different areas offer so many different sites and sounds to explore (all within one respective country). I'd like to visit more of Indonesia and also more of SE Asia. It appears to be a beautiful part of the world.
Yes, I agree that all the SE Asian countries have a lot to offer, even within their own states (with the exception of Singapore, which is a city-state). Indonesia is so huge and so beautiful that each trip there is a different experience, every single time.