I've never thought about this before. I can't say I have a favourite bridge, but I prefer old stone country style bridges that you find in parks, and have small streams flow under them as a opposed to monumental big city bridges that are used for driving over.
I have always had a soft spot for Sydney Harbour Bridge, or "the old coathanger" as my mother calls it, but my favourite bride is the Anzac Bridge. I just love driving over it, especially at night time, it's steel structure speaks to me somehow, telling stories of aesthetic wonder.
I was thinking of watching the movie "Bridges of Madison County" and saw your question which made me smile. There are small bridges spread throughout Central Park in New York City which are gorgeous. Each bridge is unique and best part is that there is no traffic except pedestrians so you can take your time to admire the features and take photos.
We went to Brisbane and I thought the Story Bridge was pretty nice.
I have seen some beautiful bridges through my travels. There are some great bridges in Montreal because it's an island. Same with New York. Same with Niagara. Probably one of the most famous ones is the Golden Gate, which is stunning to look at. The list is endless. My favourite is the one that takes me from one starting point to the other safely.
Kurilpa Bridge across the Brisbane River is quite new and it has won awards for its unique design. It is only accessible by bike or on foot and at night it is lit by rainbow LED lights - very pretty and worth a visit next time you're in town.
I have so much respect for the complicated engineering that goes into bridge building which is the life-line of communication by road. Some of the old wooden bridges that cross rivers in the South West of WA were built by horse and cart. Never-the-less, they still had clever designers who understood complex physical forces and designed them to sustain... through generations of use. They are lovely to see, but you need to get out of your car and view them from underneath....a little thought to the grueling work of our pioneers. For me the most exciting bridge in my area is the newish bridge made from steel at Giant Forest Walk at the Valley of the Giants. Its looks light, elegant with a lovely balance of fragility and strength (both at the same time).. most respectful to all the giant timber that surrounds it. When I look at a bridge I try to work out..... from which bank, it reached out first.
The marvellous one is in St petersberg Russia - Nearly 5 of the bridges are opened one by one welcoming tourist with crackers and all types of illuminations and decors in the harbour and the nearby. I had a tour call WHITE NIGHT tour there and was able to assist it. The white night last for one week in June it is 24hrs/24 day you can even see flies at 10p.m