The most important thing about your site would be content that appeals to alot of people. If you want to be successful and earn a lot of revenue from your ads you need a good idea on what you want to say, how you will say it and how much time you are willing to spend on it.
Imagine you would make a site about the technological advancements made in 1750 or a site about girls showing their boobs. Well it’s easy to see wich one would become the most popular when you visit Alexa. Alexa is a site wich shows you the most popular sites across the globe. Go to http://www.alexa.com/site/ds/top_500?qterm and put either of the sites you found to compare in the search box. The results will tell you the rankings of the sites and will clearly show what topic is more appealing.
A good idea is also to check what the most used keywords are for google or yahoo
Here is a short list of popular keywords.
6 games play
8 game cheats for ps2
11 paris hilton
13 antonella barba
14 anna nicole smith
15 ps 2 game cheats
17 britney spears
19 jenna jameson
A handy tool is http://www.google.com/sktool/# , it searches popularity versus copetition for every keyword.
So writing something about these subjects might be a good idea as they are searched the most worldwide.
Also make sure you are intrested in your subjects as well. Writing about something you don't care, can drop the quality of your articles. Make it intresting for you and your readers.