Reddit mentions of Overstreet Comic Book Price Guide Volume 44

Definitely invest in some bags and boards to store these books. You can pick them up at your local comic shop or buy them online. Their value depends on their condition on the standard 1-10 grading scale used for determining the value of comics.

Since you have books of this value, I'd also recommend buying this for an accurate idea about what they are worth:

http://www.amazon.com/Overstreet-Comic-Book-Price-Guide/dp/1603601589/ref=sr_1_1?ie=UTF8&qid=1425215129&sr=8-1&keywords=comic+book+price+guide

From the ones I can see in your picture:

X-Men 1:
$1,000 for 1.0; $2,000 for 4.0; $3,000 for 6.0; $10,000 for 8.0; $23,000 for 9.0; $42,000 for 9.2

Fantastic Four 25 & 26:
$63 for 1.0; $126 for 4.0; $189 for 6.0; $504 for 8.0; $1,140 for 9.0; $1,775 for 9.2

You've got a goldmine here buddy. If you're interested in selling, you should think about getting the more valuable issues graded by CGC:

http://www.cgccomics.com/grading/

Getting your comics graded will make your selling process easier and allow your customer to know the condition of what they are buying. If your X-Men 1 is in good shape, it will be worth even more
if you get it graded.