1. In my opinion, the Old Man and the Sea is the most interesting novel.
2. I think the Old Man and the Sea is the most interesting novel.
3. As for me, the Old Man and the Sea is the most interesting novel.
4. _________, the Old Man and the Sea is the most interesting novel.
[Are the first three sentences the same? Do you have some more similar expressions?]
Yes, the first three sentences mean approximately the same thing. These are the best versions of the idea you're expressing
You could also write any of these, but they're not as good as 1, 2, or 3 above.
For me, ...
In my mind, ...
In my experience, ...
(and I'm sure there are others!)