çok teşekkürler. Onu seviyorum. (I love it) or would be 'Bunu seviyorum.' more appropriate?
On a second thought: Would you say such a thing at all in Turkish in this specific context? It might be a rather English way of expression. I wouldn't say such thing in some other languages I can think of:
German: - I like it. (Ich mag das. / Mir gefällt das.) - Great (Super! / Toll!) French: - I adore this (J'adore ( ça)) Dutch: - Great/ mighty (Geweldig!) Arabic: - Sweet (Halu ) - Great (azeem) - maybe: I like it (da ajibni)
So what would be appropriate in Turkish?
actually, we would rather use past tense in Turkish, "bunu sevdim!" :) It is a bit strange I know. For example if I see your new dress, I would also say "elbiseni beğendim!" and never ever "elbiseni beğeniyorum or beğenirim". We would only use these two when we talk about something more general, when we already know this dress exists for example. If you are going to say "I like your red dress, you should wear it tomorrow", then use "beğeniyorum".
You can say both. If you say "Bunu seviyorum", to me it sounds like you are showing me a specific thing and pointing out this. "Onu seviyorum" is more like about people or living things. However, these are not very strict rules, there are cases you can use both, or you can use in other conditions. Gramatically both are correct and do not sound very English :)
Just a note: If you have questions about something other than the sentence above, it is better to open another discussion, since usually only people who do not understand this sentence are checking this title :) It is also easier for us to distinguish between sentence discussions and others.
Hope these will help! Good luck learning!