I really like the minimalist approach. I don't think it loses its effect either. It's just a little hit and miss. When you have an all-white frontcover it brings much attention to the front artwork, which can make it very hard to choose the right image. But it's also a matter of personal taste I guess and other users might disagree with me.
Personally I really like your Abe's Oddysee, Dragon Valor, Worms, Bushido Blade and Jade Cocoon covers. They just click with me. I don't know exactly what it is but I think they're great. Although I think there are far better dragon images to use than the one on Dragon Valor but that is just lamenting on a high level

All in all these covers are very good work!
On the other hand I think the frontcovers for Tales of Destiny 2, Vandal Hearts, Worms Armageddon and the Alundra games are very bland and very generic. Apart from Worms Armageddon there's so much artwork to be found on the net for these games for some really awesome covers. Right now they look very unspectacular and exchangable.
I'm not slamming your work
Mr. Ben. You've put time and effort into this and I do appreciate it. I just wanted to give you some feedback which you can ignore or take into consideration on your future covers.