Hello,

1.First of all, you must define your business/marketing objective for this game app. Is this app designed for you to make money or reach users? You must be clear on what you intend your Game app to achieve for you.
From what I see you post here, it seemed to me that your main objective is to reach more users and get lots of downloads for your app. In that case you fall in the category of developers known as "Hunters". In your case, revenue is equally as important as reach and this is reflected in youor choice of iOS as your priority platform. Indeed iOS offers better revenue opportunities.

2. Secondly, having determined your business objective, then you move to the next question. Who is your audience? In this case, you want to target the gamers "sporty and aggressive" niche.
Now, I recommend you visit the Apple store and check the top free, top paid and top grossing charts in the " games"category that you are interested in. In your own case, you better be looking at the "top paid" and "grossing" charts since your main objective is REACH and REVENUE.

3. I suggest your check Google Trends and use the right keyword to see what Games apps are currently TRENDING. This way, you will look at FEATURES of such games to get User Interface devlopement ideas.
You must also give yourself to learning about SEO(Search engine optimization) principles, policies and best practices as it relates to the Apple store.

4. Also check Facebook Games section for developers. I bet you will get cool ideas on User Interface design and codes that will give your maximum REACH
Check for games that are TRENDING on facebook . See https://www.facebook.com/games/browse/top for facebook "Top Charts" games. I can guarantee you that most Facebook Games apps are supported on iOS and also available on the Apple store. These games will give you great User Interface design ideas.

Games apps reach do not depend only on User Interface design, so get into the SEO & Analytics part of the Apple store market place for wise use of "keywords".

Cheers & Have a nice week ahead.

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Suggested examples reached by entering "racing" in the Game section of Facebook Games Apps (https://www.facebook.com/games/browse/adventure)

https://www.facebook.com/realracing

Try out a few of these games on your iPad and check out their user experience, which is a key factor for maximum user ENGAGEMENT.

You don't need to spend 6 months on building anything new to validate this. Creating design mockups of another variation that has a white sleek look will be enough to canvas opinions.

It is fairly inexpensive to run a test via google consumer surveys or similar to hit a large chunk of your target demographic with a "which would you buy" type question.

I wouldn't worry about getting it into stores for now. If you success in building a quality product that the market wants you won't struggle for a sales platform.

Users don't really care if an element in the game looks more "Apple" but Apple cares. If you make a fun game users will play the game and tell them friends about it. If you incorporate features that Apple wants showcased and graphically build the game to fit in with iOS7 you have a better chance to get featured by Apple which will get your game more visible.

You need to decide which features you are implementing for the user and what you are implementing for the OEM. Also, Apple will care more about your game if you incorporate and Apple iOS feature more than the design and look.