Firstly, it's great to see that you're asking the right question rather than "how can I manipulate rankings"! Your head is definitely in the right space.
It sounds like you've probably already seen it but Rand did cover this in a Whiteboard Friday a little while back too. Offering unique value doesn't necessarily mean that you have to come up with a complete game-changer where you do something radically different to the rest of your industry (though that certainly doesn't hurt either!), it's about giving the users what they're looking for in the simplest way possible.
For me, the best way to do this is to look around at the first couple of pages of competitors to see what they're doing right and compile a list. Then, ignore what you've got on the current and walk through the process you'd want to take as a user. For a service like yours, I'd be walking myself through a hypothetical situation where I wanted to take a bike tour somewhere I've never been and writing down all the questions I'd want answered.
For example, "if I was visiting Rome and wanted to take a bike tour around the Colosseum, what would I want to know? I find this helpful because when you know everything about your particular service, it's hard to effectively put yourself in the shoes of a prospective customer.
In answer to my hypothetical question, I would come up with answers like:
- What do they look like?
- How much?
- How do I book?
- What hours are they open for pickup/drop-off?
- What if I get lost and miss the cut-off for returns?
- Are there guided tours?
- Do you have phone mounts or GPS units so I don't get lost?
- Can you offer pre-mapped routes for me to follow and see interesting things?
- What if the bike breaks?
- What if it gets stolen?
The list would go on but spend a good amount of time thinking about these things and not only answer what you'd need to know but also what would be great if you could have. This could even spark new ideas that could set your business apart from the others.
Once you've got all of this together, the final challenge is working out the best way to present this information to users without making them trawl through three thousands words of content to find what they're looking for. Get creative and answer questions in various ways. Rather than relying on a large block of content describing bikes for example, have a handful of hi-res photos of them right there on your home page and the key characteristics pointed out.
Don't forget, this sort of service is all about fun and excitement so be sure to build the user experience around that sort of a vibe - users should be excited to throw money at you after looking at your website.
Hope that helps!