Chelsea's success was the most straightforward, coming in regulation fashion against struggling Bundesliga outfit Schalke, but Arsenal's perhaps the most impressive given that it ended a lengthy home unbeaten run of Borussia Dortmund.
Sky Bet cut Arsenal to 16/1 as a result of their victory, one which keeps them top of Group F and in a strong position to qualify for the 11th consecutive season under Arsene Wenger.
Chelsea are considered more likely winners alongside Manchester City at 14/1, while Manchester United, who welcome Arsenal in the Premier League on Sunday, are alongside them at 16/1.
Bayern Munich remain 5/2 favourites after they joined City in the last-16 with a narrow victory on Tuesday, but Barcelona were cut to 9/2 after joining them with a 3-1 win over AC Milan a day later.
Real Madrid are third in the betting at 5/1 with PSG and Atletico completing the group at 14/1.
Sky Bet's Sandro Di Michele said: "That was a superb result for Arsenal and although they still have work to do, it looks like they'll yet again qualify for the last 16 of the Champions League.
"With City through and both United and Chelsea likely to join them, we find it difficult to split the Premier League sides as while Arsenal are the ones with the most work to do, as every week passes we have to take them more and more seriously.
"As far as this week's results go, we gave back some of Tuesday's profit with Barcelona, Atletico, Napoli and Chelsea making up the spine of most accumulators on Wednesday."