Seti, no offense, but in a medium such as a forum (or a medium such as speech or any communication in general), it is or should be automatically understood that whatever the user communicates, it is their opinion. To have to preface one's post with "In my opinion," or "To my way of seeing it," or "Through my subjective world-view" is totally and completely redundant. We, as subjective human beings, do not speak Fact and Raw Objectivity.
If somebody says, "Oblivion was bland" (or hell, "Morrowind was bland," or "Triple-chocolate-peanut-butter brownies are bland"), then they have put forth an opinion.
If you or someone else says, "Oblivion was not bland," or "Morrowind was not bland," or "Triple-chocolate-peanut-butter brownies are not bland", then you or they are putting forth an opinion.
In neither case is one required to specify, "Oh, but this is just my opinion," because that is implicit by the very definition of what it means to open one's mouth (or extend one's fingers to the keyboard) and proclaim anything at all.