SQ's lounge footprint across its network is not a benchmark amongst airlines as it lacks the elegance that you find at Cathay's The Pier and Deck and soon The Wing (once the new design is unveiled).
Having said this, SQ lounges are functional and predictable but nothing outstanding.

My votes goes to #1 - Cathay Pacific (The Pier - First and Business and The Deck), #2 - Qantas (First - SYD/MEL/SIN) and #3 - Qatar (First and Business in Doha) for their premium lounge products.