So first off this is a common question amongst many "new" developers.
How to get noticed in such a crowded market?
Well, there are a number of ways to get noticed and get your game out there.
The first is paid advertisement
If you have a $ to throw into a marketing campaign it could be beneficial( get you downloads and help you rank higher in the charts).
However, you must make sure you spend your money strategically. Invest in banners on popular mobile websites. I believe on a lot of popular websites you can get a banner ad up for a week for a few hundred dollars. I have known this to work for many friend developers and for myself in the past. But of course, you have to be willing to spend the money.
You can also invest in banner ads such as admob, chartboost etc. Note, that there is not a 100% chance that these will work in your favor and your money will be well invested.
This is the gamble with paid marketing.
The next is
This is the more difficult marketing option between the two.(For obvious reasons).
Free marketing consists of posting on forums(Remember: You should be an active member of these forums, or else you'll just appear as a spammer and be ignored).
Posting in facebook groups. Sharing with friends and family. Using social media. Contacting the press. Contacting bloggers who blog about games.
While all of these are effective, you need to begin building a community or fan base from DAY ONE. You need to be able to contact the people who download your game by having them opt in to a online forum community, or have them opt in to a facebook group community.
This is important to do and important to incentivize it such as unlocking a bonus level by liking a facebook page or group.
I did a video about this on my youtube channel a few days ago actually.(Link in signature)
Hope this helps.