There are many types of decking on the market and generally, as with most things, you get what you pay for.
At the bottom rung of the ladder is pressure treated softwood. If you are prepared to look after it then a softwood deck should last many years. If you are prepared to look after it. There are a variety of products that will keep the algae at bay and a huge range stains and varnishes.
Hardwoods look lovely and will also last a long time and can generally be left untreated allowing the deck to fade to a silvery grey. They will get slippery though.
Nowadays we usually specify and install wood composites. As well as looking great these products will last for decades and are manufactured to be anti-slip. Some types are made entirely from recycled materials.