don't always take me away from adding a game to the list. when i search a game put a thumbnail of it then the text beside it with a check box. this will allow me to add it and not be taken away from the main page.
I'm not sure I understand what you mean here. When you type a search and press enter (or click the magnifier), you are taken to a list of all results, with a miniature and a checkbox that you can use to either add the game to your collection or wishlist, while staying on the result page.
have a deeper extended game list. i was trying to add assassins creed. not found. this game has been around for nearly 10 years.
Maybe you didn't press enter when you typed a search? Because as mentioned by Fazerco, there are a LOT of results for Assassin's Creed. And when you really don't find an entry after searching for it, you can just add it yourself; this is what makes VGCollect stand out from most other collection sites, the ability to contribute to the database.
ability to add by platform. allow me to check a box to search by platform by default. i have lots of xbox and ps3 games. and i not wish to scroll down and find it everytime. thats way more involved then it needs to be.
When you click "Browse" at the top (between "Sell List" and "Forum"), you can choose a platform and see everything in the database for that particular platform. If you mean that you want to make a search and limit it to a platform, you can hover the search button and click "Advanced" under the typing box. Or you can click here:
http://vgcollect.com/search.
I hope that my answer can help you understand a bit more how the site works, and that it will help you enjoy it better!
If you want more tips and help, I strongly suggest reading the Style guide:
http://vgcollect.com/forum/index.php/topic,22.0.html. This will help you find results more easily, as well as improve your own submissions if you end up submitting new ones.