The 30-year-old missed large chunks of the previous two campaigns with injuries and netted just three goals for the Whites last season. Johnson has already equalled that tally this season, scoring against NSI Runavik, Crusaders and in Thursday's 2-0 victory over RNK Split in the Europa League third qualifying round.
"Sharp and in good form - that is the way I always saw him when I was working in England," Jol said after the match. "He is a very good player, lively and he can play the ball too."
The former Spurs boss added: "He can also do something in an individual way like he did with (winning) the penalty kick so I can't ask for more. If he stays fit then he is a great player for us."
Reports emanated on Thursday that West Ham manager Sam Allardyce was lining up a £2million bid for the striker, whose contract runs out at the end of the season.
When asked about the Hammers' interest, Jol retorted: "It's always the same, there's always interest in five or six players. Maybe you don't know about that but now you do you start talking about it. People will always talk because we have got good players."
A first-half effort from Johnson set the west Londoners' on their way to victory at Craven Cottage.
Fulham endured a frustrating night in Croatia last week as they struggled to a goalless draw against Split, but they managed to see off the Reds on home soil. Johnson's header proved the only goal of a first half in which the west Londoners dominated, before skipper Danny Murphy put the tie beyond doubt from the spot in a challenging second half.
Fulham will find out their next opponents in Friday afternoon's draw and Jol will now prepare his troops for the opening match of the Barclays Premier League a week on Saturday. Aston Villa are the opponents and the Dutchman admits preparations have been far from ideal due to their Europa League commitments.
"We could organise another game for next Tuesday but I think that's a bad idea," he added. "We have played six games now. Maybe you would prefer to play eight or nine games in the pre-season as some other players didn't play a lot so that is probably a disadvantage, but I am satisfied with the results because we got through to the next round."
Source: PA