Someone asked me this once. My answer, which is still the same today, is that Suchet for me is best in the shorter 1 Hour episodes of Poirot. I think Ustinov and Finney do better in the movie versions of Poirot. Most of Suchet's tv movies, at least for me, didn't turn out that great compared to Ustinov and Finney's versions.
I think it may have been the Partners in Crime from the 1980s. I remember liking it but not loving it, and thinking it was a bit silly...but yet going back each week to watch the next one (PBS Boston). I had been a Christie fan, since my teen years, from reading the books. Over time I have come to appreciate Partners series more--especially after seeing some of the 21st century adaptations.